function Sandcrawler($scope) {
  $scope.location = "Mos Eisley North";
  $scope.move = function(newLocation) {
    $scope.location = newLocation;
  }
}
function Droid($scope) {
  $scope.sell = function(newLocation) {
    $scope.location = newLocation;
  }
}

<div ng-controller="Sandcrawler">
  <p>Location: {{location}}</p>
  <button ng-click="move('Mos Eisley South')">Move</button>
  <div ng-controller="Droid">
    <p>Location: {{location}}</p>
    <button ng-click="sell('Owen Farm')">Sell</button>
  </div>
</div>

function Sandcrawler($scope) {
  $scope.obj = {location:"Mos Eisley North"};
}
function Droid($scope) {
  $scope.summon = function(newLocation) {
    $scope.obj.location = newLocation;
  }
}

<div ng-controller="Sandcrawler">
  <p>Sandcrawler Location: {{location}}</p>
  <div ng-controller="Droid">
    <button ng-click="summon('Owen Farm')">
      Summon Sandcrawler
    </button>
  </div>
</div>

function Sandcrawler($scope) {
  $scope.location = "Mos Eisley North";
  $scope.$on('summon', function(e, newLocation) {
    $scope.location = newLocation;
  });
}
function Droid($scope) {
  $scope.location = "Owen Farm";
  $scope.summon = function() {
    $scope.$emit('summon', $scope.location);
  }
}

<div ng-controller="Sandcrawler">
  <p>Sandcrawler Location: {{location}}</p>
  <div ng-controller="Droid">
    <p>Droid Location: {{location}}</p>
    <button ng-click="summon()">Summon Sandcrawler</button>
  </div>
</div>

function Sandcrawler($scope) {
  $scope.location = "Mos Eisley North";
  $scope.recall = function() {
    $scope.$broadcast('recall', $scope.location);
  }
}
function Droid($scope) {
  $scope.location = "Owen Farm";
  $scope.$on('recall', function(e, newLocation) {
    $scope.location = newLocation;
  });
}

<div ng-controller="Sandcrawler">
  <p>Sandcrawler Location: {{location}}</p>
  <button ng-click="recall()">Recall Droids</button>
  <div ng-controller="Droid">
    <p>Droid Location: {{location}}</p>
  </div>
</div>

function Sandcrawler($scope) {
  $scope.$on('requestDroidRecall', function(e) {
    $scope.$broadcast('executeDroidRecall');
  });
}
function Droid($scope) {
  $scope.location = "Owen Farm";
  $scope.recallAllDroids = function() {
    $scope.$emit('requestDroidRecall');
  }
  $scope.$on('executeDroidRecall', function() { 
    $scope.location = "Sandcrawler"
  });
}

<div ng-controller="Sandcrawler">
  <div ng-controller="Droid">
    <h2>R2-D2</h2>
    <p>Droid Location: {{location}}</p>
    <button ng-click="recallAddDroids()">Recall All Droids</button>
  </div>
  <div ng-controller="Droid">
    <h2>C-3PO</h2>
    <p>Droid Location: {{status}}</p>
    <button ng-click="recallAddDroids()">Recall All Droids</button>
  </div>
</div>

var app = angular.module('myApp', []);
app.factory('instance', function(){
  return {};
});
app.controller('MainCtrl', function($scope, instance) {
 $scope.change = function() {
    instance.name = $scope.test;
 };
});
app.controller('sideCtrl', function($scope, instance) {
  $scope.add = function() {
    $scope.name = instance.name;
  };
});

<div ng-controller="MainCtrl">
   <input type="text" ng-model="test" />
   <div ng-click="change()">click me</div>
</div>
<div ng-controller="sideCtrl">
  <div ng-click="add()">my name {{name}}</div>
</div>