Referencing "the app" and venting with Marionettejs...

app.js

define(function (require) {
	//require dependancies
	var Marionette = require('backbone.marionette');
	var Backbone = require('backbone');
	var $ = require('jquery');
	var _ = require('underscore');


	// Override renderer to use pre-compiled templates
	Marionette.Renderer.render = function (template, data) {
		return template(data);
	};

	// Create, configure, and return application object
	var app = new Marionette.Application();

	app.addRegions({
		mainRegion: '#main'
	});

	app.addInitializer(function (options) {
		this.router = options.router;
		this.models = new Backbone.Model();
		this.views = new Backbone.Model();
	});

	app.on('initialize:after', function () {
		$(function () {
			Backbone.history.start();
		});
	});

	return app;
});

controller.js

define(function (require) {
	var app = require('app/app');
	var MyView = require('views/myView');
	
	app.addInitializer(function () {});
	var controller = {
		showView: function showView(){
			app.mainRegion.show(new MyView({ model: new Backbone.Model({'prop':'value'}) }));
		}
	}
	
	return controller;
});

mySubView.js

define(function (require) {
	var app = require('app/app');
	
	return Marionette.ItemView.extend({
	        template: '#MySubView',
	        events: {
	            'click #button': 'sendClick'
	        },
	        
	        triggers: {
	            'afterClick': 'afterClick'
	        },
	        
	        initialize: function initialize(){
	            this.on('afterClick', this.afterClick);
	        },
	
	        sendClick: function(e) {
	            e.preventDefault();
	            console.log('Good... Use your ventful capabilities boy...');
	            //trigger some method in the parent...
	            this.trigger('processClick');
	        },
	        
	        afterClick: function(who) {
	            console.log("I've been waiting for you... The circle is now complete. When I left you I was the but the sender, now I am the receiver...", who);
	        }
	});
});

myView.js

define(function (require) {
	var app = require('app/app');
	var MySubView = require('views/mySubView');
	
	return Marionette.Layout.extend({
	        template: '#MyView',
	        views: {},
	        regions: {
	            myRegion: '#myRegion'
	        },
	        
	        onShow: function onShow(){
	            this.views.mySubView = new MySubView({ model: this.model }).on('processClick', this.sendBackClick, this);
	            this.myRegion.show(this.views.mySubView);
	        },
	        
	        sendBackClick: function(){
	            //do some stuff, then, let the child know you're done...
	            console.log('heh heh heh heh.... Goood, goooood! Your triggers have made you powerful. Now, fulfil your parents destiny and take the event at my side!!!');
	            //use trigger?
	            this.views.mySubView.trigger('afterClick', 'from trigger');
	            //call method directly?
	            this.views.mySubView.afterClick('called directly');
	        }
	});
});