diff --git a/Sources/FirebladeECS/ManagedContiguousArray.swift b/Sources/FirebladeECS/ManagedContiguousArray.swift
index b3a1256..f9a985d 100644
--- a/Sources/FirebladeECS/ManagedContiguousArray.swift
+++ b/Sources/FirebladeECS/ManagedContiguousArray.swift
@@ -17,6 +17,7 @@ public protocol ManagedContiguousArrayProtocol: class {
 	associatedtype Element
 	static var chunkSize: Int { get }
 	init(minCount: Int)
+	var count: Int { get }
 	func insert(_ element: Element, at index: Int)
 	func has(_ index: Int) -> Bool
 	func get(at index: Int) -> Element?
@@ -27,15 +28,23 @@ public class ManagedContiguousArray: ManagedContiguousArrayProtocol {
 	public static var chunkSize: Int = 4096
 
 	public typealias Element = Any
+	var _count: Int = 0
 	var _store: ContiguousArray<Element?> = []
 	public required init(minCount: Int = chunkSize) {
 		_store = ContiguousArray<Element?>(repeating: nil, count: minCount)
 	}
 
+	public var count: Int {
+		return _count
+	}
+
 	public func insert(_ element: Element, at index: Int) {
 		if needsToGrow(index) {
 			grow(including: index)
 		}
+		if _store[index] == nil {
+			_count += 1
+		}
 		_store[index] = element
 	}
 	public func has(_ index: Int) -> Bool {
@@ -48,6 +57,9 @@ public class ManagedContiguousArray: ManagedContiguousArrayProtocol {
 	}
 
 	public func remove(at index: Int) {
+		if _store[index] != nil {
+			_count -= 1
+		}
 		return _store[index] = nil
 	}
 
diff --git a/Sources/FirebladeECS/Nexus+Component.swift b/Sources/FirebladeECS/Nexus+Component.swift
index 916e5db..8c5e1db 100644
--- a/Sources/FirebladeECS/Nexus+Component.swift
+++ b/Sources/FirebladeECS/Nexus+Component.swift
@@ -7,6 +7,14 @@
 
 extension Nexus {
 
+	public var numComponents: Int {
+		var count = 0
+		for (_, value) in componentsByType {
+			count += value._count
+		}
+		return count
+	}
+
 	public func has(componentId: ComponentIdentifier, entityIdx: EntityIndex) -> Bool {
 		guard let uniforms = componentsByType[componentId] else { return false }
 		return uniforms.has(entityIdx)
diff --git a/Sources/FirebladeECS/Nexus+Entity.swift b/Sources/FirebladeECS/Nexus+Entity.swift
index 0fc534c..1c32974 100644
--- a/Sources/FirebladeECS/Nexus+Entity.swift
+++ b/Sources/FirebladeECS/Nexus+Entity.swift
@@ -7,9 +7,13 @@
 
 extension Nexus {
 
+	public var entities: [Entity] {
+		return entityStorage.filter { $0.isValid }
+	}
+
 	fileprivate func nextEntityIdx() -> EntityIndex {
 		guard let nextReused: EntityIdentifier = freeEntities.popLast() else {
-			return entities.count
+			return entityStorage.count
 		}
 		return nextReused.index
 	}
@@ -17,8 +21,8 @@ extension Nexus {
 	public func create(entity name: String? = nil) -> Entity {
 		let newEntityIndex: EntityIndex = nextEntityIdx()
 		let newEntityIdentifier: EntityIdentifier = newEntityIndex.identifier
-		if entities.count > newEntityIndex {
-			let reusedEntity: Entity = entities[newEntityIndex]
+		if entityStorage.count > newEntityIndex {
+			let reusedEntity: Entity = entityStorage[newEntityIndex]
 			assert(reusedEntity.identifier == EntityIdentifier.invalid, "Stil valid entity \(reusedEntity)")
 			reusedEntity.identifier = newEntityIdentifier
 			reusedEntity.name = name
@@ -26,15 +30,15 @@ extension Nexus {
 			return reusedEntity
 		} else {
 			let newEntity = Entity(nexus: self, id: newEntityIdentifier, name: name)
-			entities.insert(newEntity, at: newEntityIndex)
+			entityStorage.insert(newEntity, at: newEntityIndex)
 			notify(EntityCreated(entityId: newEntityIdentifier))
 			return newEntity
 		}
 	}
 
 	/// Number of entities in nexus.
-	public var count: Int {
-		return entities.count - freeEntities.count
+	public var numEntities: Int {
+		return entityStorage.count - freeEntities.count
 	}
 
 	func isValid(entity: Entity) -> Bool {
@@ -44,7 +48,7 @@ extension Nexus {
 	func isValid(entity entitiyId: EntityIdentifier) -> Bool {
 		return entitiyId != EntityIdentifier.invalid &&
 			entitiyId.index >= 0 &&
-			entitiyId.index < entities.count
+			entitiyId.index < entityStorage.count
 	}
 
 	public func has(entity entityId: EntityIdentifier) -> Bool {
@@ -52,7 +56,7 @@ extension Nexus {
 	}
 
 	public func get(entity entityId: EntityIdentifier) -> Entity {
-		return entities[entityId.index]
+		return entityStorage[entityId.index]
 	}
 
 	@discardableResult
@@ -70,7 +74,7 @@ extension Nexus {
 
 		// replace with "new" invalid entity to keep capacity of array
 		let invalidEntity = Entity(nexus: self, id: EntityIdentifier.invalid)
-		entities[entityId.index] = invalidEntity
+		entityStorage[entityId.index] = invalidEntity
 
 		freeEntities.append(entityId)
 
diff --git a/Sources/FirebladeECS/Nexus+Family.swift b/Sources/FirebladeECS/Nexus+Family.swift
index 1456c81..0ee1c2e 100644
--- a/Sources/FirebladeECS/Nexus+Family.swift
+++ b/Sources/FirebladeECS/Nexus+Family.swift
@@ -71,7 +71,7 @@ extension Nexus {
 		assert(replaced == nil, "Family with exact trait hash already exists: \(traitHash)")
 
 		// FIXME: this is costly for many entities
-		for entity: Entity in entities {
+		for entity: Entity in entityStorage {
 			update(membership: family, for: entity.identifier)
 		}
 
diff --git a/Sources/FirebladeECS/Nexus.swift b/Sources/FirebladeECS/Nexus.swift
index 4a70e79..f4674c1 100644
--- a/Sources/FirebladeECS/Nexus.swift
+++ b/Sources/FirebladeECS/Nexus.swift
@@ -24,7 +24,7 @@ public class Nexus {
 
 	/// - Index: index value matching entity identifier shifted to Int
 	/// - Value: each element is a entity instance
-	var entities: Entities
+	var entityStorage: Entities
 
 	/// - Key: component type identifier
 	/// - Value: each element is a component instance of the same type (uniform). New component instances are appended.
@@ -42,11 +42,11 @@ public class Nexus {
 	var freeEntities: ContiguousArray<EntityIdentifier>
 
 	var familiyByTraitHash: [FamilyTraitSetHash: Family]
-	var familyMembersByTraitHash: [FamilyTraitSetHash: [EntityIdentifier]]
+	var familyMembersByTraitHash: [FamilyTraitSetHash: [EntityIdentifier]] // SparseSet for EntityIdentifier
 	var familyContainsEntityId: [TraitEntityIdHash: Bool]
 
 	public init() {
-		entities = Entities()
+		entityStorage = Entities()
 		componentsByType = [:]
 		componentIdsByEntity = [:]
 		componentIdsByEntityLookup = [:]
diff --git a/Sources/FirebladeECS/SparseSet.swift b/Sources/FirebladeECS/SparseSet.swift
new file mode 100644
index 0000000..b51995b
--- /dev/null
+++ b/Sources/FirebladeECS/SparseSet.swift
@@ -0,0 +1,68 @@
+//
+//  SparseSet.swift
+//  FirebladeECS
+//
+//  Created by Christian Treffs on 30.10.17.
+//
+
+public struct SparseComponentSet<Element: Component> {
+	fileprivate typealias ComponentIdx = Int
+	fileprivate typealias EntryTuple = (entityId: EntityIdentifier, component: Element)
+	fileprivate var dense: ContiguousArray<EntryTuple?>
+	fileprivate var sparse: [EntityIdentifier: ComponentIdx]
+
+	public init(_ min: Int = 1024) {
+		dense = ContiguousArray<EntryTuple?>()
+		dense.reserveCapacity(min)
+
+		sparse = [EntityIdentifier: ComponentIdx](minimumCapacity: min)
+	}
+
+	public var count: Int { return dense.count }
+	internal var capacitySparse: Int { return sparse.count }
+	internal var capacityDense: Int { return dense.count }
+
+	public func contains(_ entityId: EntityIdentifier) -> Bool {
+		guard let compIdx: ComponentIdx = sparse[entityId] else { return false }
+		return compIdx < count && dense[compIdx] != nil
+	}
+
+	@discardableResult
+	public mutating func add(_ element: Element, with entityId: EntityIdentifier) -> Bool {
+		if contains(entityId) { return false }
+		sparse[entityId] = count
+		let entry: EntryTuple = EntryTuple(entityId: entityId, component: element)
+		dense.append(entry)
+		return true
+	}
+
+	public func get(_ entityId: EntityIdentifier) -> Element? {
+		guard let compIdx: ComponentIdx = sparse[entityId] else { return nil }
+		return dense[compIdx]?.component
+	}
+
+	public mutating func remove(_ entityId: EntityIdentifier) -> Element? {
+		guard let compIdx: ComponentIdx = sparse[entityId] else { return nil }
+		dense.swapAt(compIdx, count-1)
+		sparse[entityId] = nil
+		let swapped: EntryTuple = dense[compIdx]!
+		sparse[swapped.entityId] = compIdx
+		let removed: EntryTuple = dense.popLast()!!
+		return removed.component
+	}
+
+	public mutating func clear(keepingCapacity: Bool = false) {
+		dense.removeAll(keepingCapacity: keepingCapacity)
+	}
+}
+
+extension SparseComponentSet: Sequence {
+
+	public func makeIterator() -> AnyIterator<Element> {
+		var iterator = dense.makeIterator()
+
+		return AnyIterator<Element> {
+			iterator.next()??.component
+		}
+	}
+}
diff --git a/Sources/FirebladeECSDemo/main.swift b/Sources/FirebladeECSDemo/main.swift
index b317ea9..1d36ccd 100644
--- a/Sources/FirebladeECSDemo/main.swift
+++ b/Sources/FirebladeECSDemo/main.swift
@@ -1,13 +1,23 @@
 import CSDL2
 import FirebladeECS
+var tFrame = Timer()
 var tSetup = Timer()
 tSetup.start()
 if SDL_Init(SDL_INIT_VIDEO) != 0 {
 	fatalError("could not init video")
 }
+
+var frameCount: UInt = 0
+var fps: Double = 0
+let nexus = Nexus()
+
+var windowTitle: String {
+	return "Fireblade ECS demo: [entities: \(nexus.numEntities), components: \(nexus.numComponents)] @ [FPS: \(fps), frames: \(frameCount)]"
+}
 let width: Int32 = 640
 let height: Int32 = 480
-let hWin = SDL_CreateWindow("Fireblade ECS demo", 100, 100, width, height, SDL_WINDOW_SHOWN.rawValue)
+let hWin = SDL_CreateWindow(windowTitle, 100, 100, width, height, SDL_WINDOW_SHOWN.rawValue)
+
 if hWin == nil {
 	SDL_Quit()
 	fatalError("could not crate window")
@@ -22,8 +32,6 @@ func randColor() -> UInt8 {
 	return UInt8(randNorm() * 254) + 1
 }
 
-let nexus = Nexus()
-
 class Position: Component {
 	var x: Int32 = width/2
 	var y: Int32 = height/2
@@ -39,20 +47,43 @@ func createScene() {
 	let numEntities: Int = 10_000
 
 	for i in 0..<numEntities {
-		let e = nexus.create(entity: "\(i)")
-		e.assign(Position())
-		e.assign(Color())
+		createDefaultEntity(name: "\(i)")
 	}
 }
 
+func batchCreateEntities(count: Int) {
+	for _ in 0..<count {
+		createDefaultEntity(name: nil)
+	}
+}
+
+func batchDestroyEntities(count: Int) {
+
+	var i = count
+	for entity in nexus.entities {
+		if nexus.destroy(entity: entity) {
+			i -= 1
+			if i == 0 {
+				return
+			}
+		}
+	}
+}
+
+func createDefaultEntity(name: String?) {
+	let e = nexus.create(entity: name)
+	e.assign(Position())
+	e.assign(Color())
+}
+
 class PositionSystem {
 	let family = nexus.family(requiresAll: [Position.self], excludesAll: [])
-	var acceleration: Double = 4.0
+	var velocity: Double = 4.0
 	func update() {
 		family.iterate(components: Position.self) { [unowned self](_, pos) in
 
-			let deltaX: Double = self.acceleration*((randNorm() * 2) - 1)
-			let deltaY: Double = self.acceleration*((randNorm() * 2) - 1)
+			let deltaX: Double = self.velocity*((randNorm() * 2) - 1)
+			let deltaY: Double = self.velocity*((randNorm() * 2) - 1)
 			var x = pos!.x + Int32(deltaX)
 			var y = pos!.y + Int32(deltaY)
 
@@ -142,6 +173,10 @@ func printHelp() {
 	+		increase movement speed
 	-		reduce movement speed
 	space	reset to default movement speed
+	e		create 1 entity
+	d		destroy 1 entity
+	8		batch create 10k entities
+	9		batch destroy 10k entities
 	"""
 	print(help)
 }
@@ -155,8 +190,12 @@ printHelp()
 tRun.start()
 var event: SDL_Event = SDL_Event()
 var quit: Bool = false
+var currentTime: UInt32 = 0
+var lastTime: UInt32 = 0
+var frameTimes: [UInt64] = []
 print("================ RUNNING ================")
 while quit == false {
+	tFrame.start()
 	while SDL_PollEvent(&event) == 1 {
 		switch SDL_EventType(rawValue: event.type) {
 		case SDL_QUIT:
@@ -172,13 +211,21 @@ while quit == false {
 			case SDLK_r:
 				positionResetSystem.update()
 			case SDLK_s:
-				positionSystem.acceleration = 0.0
+				positionSystem.velocity = 0.0
 			case SDLK_PLUS:
-				positionSystem.acceleration += 0.1
+				positionSystem.velocity += 0.1
 			case SDLK_MINUS:
-				positionSystem.acceleration -= 0.1
+				positionSystem.velocity -= 0.1
 			case SDLK_SPACE:
-				positionSystem.acceleration = 4.0
+				positionSystem.velocity = 4.0
+			case SDLK_e:
+				batchCreateEntities(count: 1)
+			case SDLK_d:
+				batchDestroyEntities(count: 1)
+			case SDLK_8:
+				batchCreateEntities(count: 10_000)
+			case SDLK_9:
+				batchDestroyEntities(count: 10_000)
 			default:
 				break
 			}
@@ -190,6 +237,28 @@ while quit == false {
 	positionSystem.update()
 
 	renderSystem.render()
+	tFrame.stop()
+
+	frameTimes.append(tFrame.nanoSeconds)
+
+	// Print a report once per second
+	currentTime = SDL_GetTicks()
+	if (currentTime > lastTime + 1000) {
+
+		let count = UInt(frameTimes.count)
+		frameCount += count
+		let sum: UInt64 = frameTimes.reduce(0, { $0 + $1 })
+		frameTimes.removeAll(keepingCapacity: true)
+
+		let avergageNanos: Double = Double(sum)/Double(count)
+
+		fps = 1.0 / (avergageNanos * 1.0e-9)
+		fps.round()
+
+		SDL_SetWindowTitle(hWin, windowTitle)
+		lastTime = currentTime
+	}
+	tFrame.reset()
 }
 
 SDL_DestroyWindow(hWin)
diff --git a/Tests/FirebladeECSTests/FamilyTests.swift b/Tests/FirebladeECSTests/FamilyTests.swift
index 5a98caf..cd92aa0 100644
--- a/Tests/FirebladeECSTests/FamilyTests.swift
+++ b/Tests/FirebladeECSTests/FamilyTests.swift
@@ -74,7 +74,7 @@ class FamilyTests: XCTestCase {
 		let family = nexus.family(requiresAll: [Position.self, Velocity.self], excludesAll: [Party.self], needsAtLeastOne: [Name.self, EmptyComponent.self])
 
 		XCTAssert(family.count == number)
-		XCTAssert(nexus.count == number)
+		XCTAssert(nexus.numEntities == number)
 
 		measure {
 			family.iterateMembers({ (entityId) in
@@ -94,7 +94,7 @@ class FamilyTests: XCTestCase {
 		let family = nexus.family(requiresAll: [Position.self, Velocity.self], excludesAll: [Party.self], needsAtLeastOne: [Name.self, EmptyComponent.self])
 
 		XCTAssert(family.count == number)
-		XCTAssert(nexus.count == number)
+		XCTAssert(nexus.numEntities	== number)
 
 		measure {
 			family.iterate(components: Velocity.self) { (_, vel) in
@@ -115,7 +115,7 @@ class FamilyTests: XCTestCase {
 		let family = nexus.family(requiresAll: [Position.self, Velocity.self], excludesAll: [Party.self], needsAtLeastOne: [Name.self, EmptyComponent.self])
 
 		XCTAssert(family.count == number)
-		XCTAssert(nexus.count == number)
+		XCTAssert(nexus.numEntities == number)
 
 		measure {
 			family.iterate(components: Position.self, Velocity.self, Name.self) { (entityId, pos, vel, nm) in
diff --git a/Tests/FirebladeECSTests/NexusTests.swift b/Tests/FirebladeECSTests/NexusTests.swift
index ced81bf..d368034 100644
--- a/Tests/FirebladeECSTests/NexusTests.swift
+++ b/Tests/FirebladeECSTests/NexusTests.swift
@@ -21,17 +21,17 @@ class NexusTests: XCTestCase {
 
 	func testCreateEntity() {
 		let nexus: Nexus = Nexus()
-		XCTAssert(nexus.count == 0)
+		XCTAssert(nexus.numEntities == 0)
 
 		let e0 = nexus.create()
 		XCTAssert(e0.identifier.index == 0)
 		XCTAssert(e0.isValid)
-		XCTAssert(nexus.count == 1)
+		XCTAssert(nexus.numEntities == 1)
 
 		let e1 = nexus.create(entity: "Named e1")
 		XCTAssert(e1.identifier.index == 1)
 		XCTAssert(e1.isValid)
-		XCTAssert(nexus.count == 2)
+		XCTAssert(nexus.numEntities == 2)
 
 		XCTAssert(e0.name == nil)
 		XCTAssert(e1.name == "Named e1")
@@ -43,28 +43,28 @@ class NexusTests: XCTestCase {
 
 	func testDestroyAndReuseEntity() {
 		let nexus: Nexus = Nexus()
-		XCTAssert(nexus.count == 0)
+		XCTAssert(nexus.numEntities == 0)
 
 		let e0 = nexus.create(entity: "e0")
 		XCTAssert(e0.isValid)
-		XCTAssert(nexus.count == 1)
+		XCTAssert(nexus.numEntities == 1)
 
 		let e1 = nexus.create(entity: "e1")
 		XCTAssert(e1.isValid)
-		XCTAssert(nexus.count == 2)
+		XCTAssert(nexus.numEntities == 2)
 
 		e0.destroy()
 
 		XCTAssert(!e0.isValid)
 		XCTAssert(e1.isValid)
-		XCTAssert(nexus.count == 1)
+		XCTAssert(nexus.numEntities == 1)
 
 		let e2 = nexus.create(entity: "e2")
 		XCTAssert(!e0.isValid)
 		XCTAssert(e1.isValid)
 		XCTAssert(e2.isValid)
 
-		XCTAssert(nexus.count == 2)
+		XCTAssert(nexus.numEntities == 2)
 
 		XCTAssert(!(e0 == e2))
 		XCTAssert(!(e0 === e2))
@@ -72,7 +72,7 @@ class NexusTests: XCTestCase {
 
 	func testComponentCreation() {
 		let nexus: Nexus = Nexus()
-		XCTAssert(nexus.count == 0)
+		XCTAssert(nexus.numEntities == 0)
 
 		let e0: Entity = nexus.create(entity: "e0")
 
@@ -145,7 +145,7 @@ class NexusTests: XCTestCase {
 		let b = nexus.create()
 		let c = nexus.create()
 
-		XCTAssert(nexus.count == 3)
+		XCTAssert(nexus.numEntities == 3)
 
 		a.assign(Position(x: 0, y: 0))
 		b.assign(Position(x: 0, y: 0))
diff --git a/Tests/FirebladeECSTests/SparseComponentSetTests.swift b/Tests/FirebladeECSTests/SparseComponentSetTests.swift
new file mode 100644
index 0000000..2595cb6
--- /dev/null
+++ b/Tests/FirebladeECSTests/SparseComponentSetTests.swift
@@ -0,0 +1,32 @@
+//
+//  SparseComponentSetTests.swift
+//  FirebladeECSTests
+//
+//  Created by Christian Treffs on 31.10.17.
+//
+
+import XCTest
+import FirebladeECS
+
+class SparseComponentSetTests: XCTestCase {
+
+	func testSet() {
+		var s = SparseComponentSet<Position>()
+
+		s.add(Position(x: 1, y: 2), with: 0)
+		s.add(Position(x: 13, y: 23), with: 13)
+		s.add(Position(x: 123, y: 123), with: 123)
+
+		for p in s {
+			print(p.x, p.y)
+		}
+
+		s.remove(13)
+
+		for p in s {
+			print(p.x, p.y)
+		}
+
+		s.remove(234567890)
+	}
+}