diff --git a/src/main/scala/com/agar/core/Agar.scala b/src/main/scala/com/agar/core/Agar.scala
index ac3b2d2..3ba8930 100644
--- a/src/main/scala/com/agar/core/Agar.scala
+++ b/src/main/scala/com/agar/core/Agar.scala
@@ -5,6 +5,7 @@ import com.agar.core.arbritrator.Arbitrator
 import com.agar.core.arbritrator.Arbitrator.Start
 import com.agar.core.context.{AgarContext, DefaultAgarContext}
 import com.agar.core.logger.Logger
+import com.agar.core.region.Region
 
 //#main-class
 
@@ -16,8 +17,10 @@ object Agar extends App {
   val logger: ActorRef = system.actorOf(Logger.props, "logger")
   val arbitrator: ActorRef = system.actorOf(Arbitrator.props(logger),"arbitrator")
 
-  arbitrator ! Start(10000)
+  // A region has a size of 4 screen 1920x1080
+  val region = system.actorOf(Region.props(arbitrator, logger, 7680, 4320), "region")
 
+  arbitrator ! Start(10000)
 }
 
 //#main-class
diff --git a/src/main/scala/com/agar/core/gameplay/energy/EnergyStatus.scala b/src/main/scala/com/agar/core/gameplay/energy/EnergyStatus.scala
new file mode 100644
index 0000000..18dc2a4
--- /dev/null
+++ b/src/main/scala/com/agar/core/gameplay/energy/EnergyStatus.scala
@@ -0,0 +1,5 @@
+package com.agar.core.gameplay.energy
+
+import com.agar.core.utils.Point2d
+
+case class EnergyStatus(position: Point2d)
diff --git a/src/main/scala/com/agar/core/gameplay/player/AreaOfInterest.scala b/src/main/scala/com/agar/core/gameplay/player/AreaOfInterest.scala
new file mode 100644
index 0000000..055bed2
--- /dev/null
+++ b/src/main/scala/com/agar/core/gameplay/player/AreaOfInterest.scala
@@ -0,0 +1,50 @@
+package com.agar.core.gameplay.player
+
+import akka.actor.ActorRef
+import com.agar.core.region.{EnergyState, PlayerState}
+import com.agar.core.utils.Vector2d
+
+// ref can be the ActorRef of the virtual or the real actor
+case class PlayerInfos(position: Vector2d, velocity: Vector2d, weight: Int, ref: ActorRef)
+
+// ref can be the ActorRef of the virtual or the real actor
+case class EnergyInfos(position: Vector2d, value: Int, ref: ActorRef)
+
+case class AOI(players: List[PlayerInfos], energies: List[EnergyInfos])
+
+
+object AreaOfInterest {
+
+  // There is overwhelming scientific evidence that the correct number is this one
+  val RADIUS_AREA_OF_INTEREST = 400
+
+  def getPlayersAOISet(players: Map[ActorRef, PlayerState], energies: Map[ActorRef, EnergyState]):  Map[ActorRef, AOI] = {
+    players.map{ case (ref, playerState) =>
+      val otherPlayers = players.filter({case (actorRef, _) => isNotTheSamePlayer(actorRef, ref) })
+      ref -> getPlayerAOI(playerState, otherPlayers, energies)
+    }
+  }
+
+  private def getPlayerAOI(playerState: PlayerState, players: Map[ActorRef, PlayerState], energies: Map[ActorRef, EnergyState]):  AOI = {
+    AOI(
+      getPlayersInAOIOfPlayer(playerState.position, players),
+      getEnergiesInAOIOfPlayer(playerState.position, energies)
+    )
+  }
+
+  private def getPlayersInAOIOfPlayer(playerPosition: Vector2d, players: Map[ActorRef, PlayerState]): List[PlayerInfos] =
+    players
+      .filter{case (_, p) => areClose(p.position, playerPosition)}
+      .map{case (r, p) => PlayerInfos(p.position, p.velocity, p.weight, r) }
+      .toList
+
+  private def getEnergiesInAOIOfPlayer(playerPosition: Vector2d, energies: Map[ActorRef, EnergyState]): List[EnergyInfos] =
+    energies
+      .filter{case (_, e) => areClose(e.position, playerPosition)}
+      .map{case (r, e) => EnergyInfos(e.position, e.value, r) }
+      .toList
+
+  private def isNotTheSamePlayer(a1: ActorRef, a2: ActorRef) = a1 != a2
+
+  private def areClose(p1: Vector2d, p2: Vector2d)  = p1.euclideanDistance(p2) <= RADIUS_AREA_OF_INTEREST
+}
\ No newline at end of file
diff --git a/src/main/scala/com/agar/core/region/Region.scala b/src/main/scala/com/agar/core/region/Region.scala
new file mode 100644
index 0000000..ed0eaae
--- /dev/null
+++ b/src/main/scala/com/agar/core/region/Region.scala
@@ -0,0 +1,88 @@
+package com.agar.core.region
+
+
+import java.util.UUID
+
+import akka.actor.{Actor, ActorRef, Props, Stash}
+import com.agar.core.context.AgarContext
+import com.agar.core.gameplay.energy.Energy
+import com.agar.core.gameplay.player.{AreaOfInterest, Player}
+import com.agar.core.gameplay.player.Player.Init
+import com.agar.core.utils.{Point2d, Vector2d}
+
+
+// TODO -- move these definitions
+
+case class PlayerState(position: Vector2d, weight: Int, velocity: Vector2d, virtual: Option[ActorRef] = Option.empty)
+
+case class EnergyState(position: Vector2d, value: Int, virtual: Option[ActorRef] = Option.empty)
+
+// ------------------------------
+
+object Region {
+
+  case object GetEntitiesAOISet
+
+  final case class InitRegion(nbOfPlayer: Int, nbOfStartingEnergy: Int)
+
+  final case class Initialized(players: Map[ActorRef, PlayerState], energies: Map[ActorRef, EnergyState])
+
+  def props(arbitrator: ActorRef, logger: ActorRef, width: Int, height: Int)(implicit agarContext: AgarContext): Props = Props(new Region(arbitrator, logger)(width, height)(agarContext))
+}
+
+class Region(arbitrator: ActorRef, logger: ActorRef)(width: Int, height: Int)(implicit agarContext: AgarContext) extends Actor with Stash {
+
+  import Region._
+
+  def MAX_ENERGY_VALUE = 10
+  def DEFAULT_VELOCITY = Vector2d(2, 2)
+  def WEIGHT_AT_START = 1
+
+
+  def id = UUID.randomUUID()
+
+  var players: Map[ActorRef, PlayerState] = Map()
+  var energies: Map[ActorRef, EnergyState] = Map()
+
+  def initialized: Receive = {
+    case GetEntitiesAOISet => sender ! AreaOfInterest.getPlayersAOISet(this.players, this.energies)
+  }
+
+  def receive: Receive = {
+    case InitRegion(nbOfPlayer, nbOfStartingEnergy) =>
+      initializeEntities(nbOfPlayer, nbOfStartingEnergy)
+      context become initialized
+      logger ! Initialized(this.players, this.energies)
+
+    case _ => stash()
+  }
+
+  def initializeEntities(nbOfPlayer: Int, nbOfStartingEnergy: Int) = {
+    val r = new scala.util.Random
+
+    this.players = (0 until nbOfPlayer)
+      .map { n =>
+        val player = freshPlayer(n)
+        val (xStart, yStart) = (r.nextInt(width), r.nextInt(height))
+        player ! Init(Point2d(xStart, yStart))
+        player -> PlayerState(Vector2d(xStart, yStart), WEIGHT_AT_START, DEFAULT_VELOCITY)
+      }.toMap
+
+    this.energies = (0 until nbOfStartingEnergy)
+      .map { _ =>
+        val id = UUID.randomUUID()
+        val position = Vector2d(r.nextInt(width), r.nextInt(height))
+        val powerOfTheEnergy = 1 + r.nextInt(MAX_ENERGY_VALUE)
+        val energy = freshEnergy(id, powerOfTheEnergy)
+        energy -> EnergyState(position, powerOfTheEnergy)
+      }.toMap
+  }
+
+  private def freshPlayer(n: Int): ActorRef = {
+    context.actorOf(Player.props(n)(agarContext.algorithm), name = s"player-$n")
+  }
+
+  private def freshEnergy(id: UUID, valueOfEnergy: Int): ActorRef = {
+    context.actorOf(Energy.props(valueOfEnergy), name = s"energy-$id")
+  }
+}
diff --git a/src/main/scala/com/agar/core/utils/Vector2d.scala b/src/main/scala/com/agar/core/utils/Vector2d.scala
index ad2e057..31f737b 100644
--- a/src/main/scala/com/agar/core/utils/Vector2d.scala
+++ b/src/main/scala/com/agar/core/utils/Vector2d.scala
@@ -1,6 +1,6 @@
 package com.agar.core.utils
 
-class Vector2d(val x: Double, val y: Double) {
+case class Vector2d(x: Double, y: Double) {
 
   def this() = this(0.0, 0.0)
 
@@ -49,6 +49,8 @@ class Vector2d(val x: Double, val y: Double) {
   /** Returns the length of the vector |a| = sqrt((ax * ax) + (ay * ay) + (az * az)) */
   def magnitude(): Double = Math.sqrt((x * x) + (y * y))
 
+  def euclideanDistance(v: Vector2d): Double = Math.sqrt(Math.pow(x - v.x, 2) + Math.pow(y - v.y, 2))
+
   def canEqual(other: Any): Boolean =
     other.isInstanceOf[Vector2d]
 
diff --git a/src/test/scala/com/agar/core/gameplay/player/AreaOfInterestSpec.scala b/src/test/scala/com/agar/core/gameplay/player/AreaOfInterestSpec.scala
new file mode 100644
index 0000000..25d5cb3
--- /dev/null
+++ b/src/test/scala/com/agar/core/gameplay/player/AreaOfInterestSpec.scala
@@ -0,0 +1,79 @@
+package com.agar.core.gameplay.player
+
+import akka.actor.{Actor, ActorSystem, Props}
+import akka.testkit.TestKit
+import com.agar.core.context.{AgarAlgorithm, AgarContext, AgarPosition, AgarSystem}
+import com.agar.core.region.{EnergyState, PlayerState}
+import com.agar.core.utils.{Point2d, Vector2d}
+import org.scalatest.{Matchers, WordSpecLike}
+
+import scala.concurrent.duration._
+
+class AreaOfInterestSpec (_system: ActorSystem)
+  extends TestKit(_system)
+    with WordSpecLike
+    with Matchers {
+
+  def this() = this(ActorSystem("AgarSpec"))
+
+  "An AreaOfInterest" should {
+    "get the list of AOI for each players" in {
+      implicit val context: AgarContext = new AgarContext {
+        override val system: AgarSystem = () => 2 seconds
+        override val position: AgarPosition = () => Point2d(0, 0)
+        override val algorithm: AgarAlgorithm = p => Point2d(p.x + 1, p.y + 1)
+      }
+
+      val playerStub1 = system.actorOf(Props(new StubActor()))
+      val playerStub2 = system.actorOf(Props(new StubActor()))
+      val playerStub3 = system.actorOf(Props(new StubActor()))
+
+      val energyStub1 = system.actorOf(Props(new StubActor()))
+      val energyStub2 = system.actorOf(Props(new StubActor()))
+
+      val players = Map(
+        playerStub1 -> PlayerState(Vector2d(100, 100), 10, Vector2d(2, 2)), // close to playerStub2
+        playerStub2 -> PlayerState(Vector2d(300, 400), 10, Vector2d(2, 2)), // close to playerStub1
+        playerStub3 -> PlayerState(Vector2d(10000, 10000), 10, Vector2d(2, 2)), // alone
+      )
+
+      val energies = Map(
+        energyStub1 -> EnergyState(Vector2d(200, 200), 10), // energy for playerStub1, playerStub2
+        energyStub2 -> EnergyState(Vector2d(9800, 9800), 10), // energy for playerStub3
+      )
+
+      val areaOfInterestSet = AreaOfInterest.getPlayersAOISet(players, energies)
+
+      areaOfInterestSet.get(playerStub1) should be (
+        Some(
+          AOI(
+            List(PlayerInfos(Vector2d(300, 400),Vector2d(2, 2), 10, playerStub2)),
+            List(EnergyInfos(Vector2d(200, 200), 10, energyStub1))
+          )
+        )
+      )
+
+      areaOfInterestSet.get(playerStub2) should be (
+        Some(
+          AOI(
+            List(PlayerInfos(Vector2d(100, 100), Vector2d(2, 2), 10, playerStub1)),
+            List(EnergyInfos(Vector2d(200, 200), 10, energyStub1))
+          )
+        )
+      )
+
+      areaOfInterestSet.get(playerStub3) should be (
+        Some(
+          AOI(
+            List.empty,
+            List(EnergyInfos(Vector2d(9800, 9800), 10, energyStub2))
+          )
+        )
+      )
+    }
+  }
+
+  class StubActor() extends Actor {
+    override def receive: Receive = { case e => sender ! e }
+  }
+}
\ No newline at end of file
diff --git a/src/test/scala/com/agar/core/region/RegionTest.scala b/src/test/scala/com/agar/core/region/RegionTest.scala
new file mode 100644
index 0000000..76f1a24
--- /dev/null
+++ b/src/test/scala/com/agar/core/region/RegionTest.scala
@@ -0,0 +1,56 @@
+package com.agar.core.region
+
+import akka.actor.{Actor, ActorRef, ActorSystem, Props}
+import akka.testkit.{TestKit, TestProbe}
+import com.agar.core.context.{AgarAlgorithm, AgarContext, AgarPosition, AgarSystem}
+import com.agar.core.region.Region.{InitRegion, Initialized}
+import com.agar.core.utils.Point2d
+import org.scalatest.{BeforeAndAfterAll, Matchers, WordSpecLike}
+
+import scala.concurrent.duration._
+
+class RegionTest (_system: ActorSystem)
+  extends TestKit(_system)
+    with Matchers
+    with WordSpecLike
+    with BeforeAndAfterAll {
+
+  def this() = this(ActorSystem("AgarSpec"))
+
+  override def afterAll: Unit = {
+    shutdown(system)
+  }
+
+  "A Region Actor" should {
+
+    "initialize a fresh region with fresh entities" in {
+      implicit val context: AgarContext = new AgarContext {
+        override val system: AgarSystem = () => 2 seconds
+        override val position: AgarPosition = () => Point2d(0, 0)
+        override val algorithm: AgarAlgorithm = p => Point2d(p.x + 1, p.y + 1)
+      }
+
+      val testProbe = TestProbe()
+      val tracer = system.actorOf(Props(new Tracer(testProbe.ref)))
+
+      val region = system.actorOf(Region.props(ActorRef.noSender, tracer, 7680, 4320), "region")
+
+      region ! InitRegion(2, 2)
+
+      val expectedCorrectInit = testProbe.expectMsgPF() {
+        case Initialized(players, energies) => {
+          players.size === 2 && energies.size === 2
+        }
+      }
+
+      expectedCorrectInit should be (true)
+    }
+  }
+
+  class Tracer(a: ActorRef) extends Actor {
+    override def receive: Receive = {
+      case e =>
+        a ! e
+    }
+  }
+}