Microservices and an API Gateway

With all the talk of Microservices, this very discussion came up in my office.
As we make services more granularized, the Client Browser becomes the focus of being the actual application: aka Single Page Application written in JavaScript: WebComponents, Angular.js, Ember.js adn the like.
This blog link is a fast read discussing at a high level the need for an API layer to hide specific implementation details from external clients, and provide an extra layer of protection from external calls.

Why Do Microservices Need an API Gateway? – @DZone