Edit in JSFiddle

angular.module('test', [])
    .controller('myController', function () {
        var vm = this;
        vm.myVar = 'Ciao';
    })
    .controller('myChildrenController', function () {
    });
<div ng-app='test'>
    <div ng-controller='myController as myCtrl'>
        <label>Modifica questo:</label>
        <input type="text" ng-model="myCtrl.myVar" />
        &raquo; {{myCtrl.myVar}}
        <div ng-controller='myChildrenController as myChildCtrl'>
            <label>Poi modifica questo:</label>
            <input type="text" ng-model="myChildCtrl.myVar" />
            &raquo;  {{myChildCtrl.myVar}}
        </div>
    </div>
</div>