At its core, Glass is a visual device. Without its heads-up optical display, people probably wouldn’t have much interest in Glass. You could tape a smartphone to the side of your face for a similar effect. Since the eyepiece makes all the difference, your applications should make every effort to present rich visual experiences. Attachments are how Glass sends and receives assets like pictures and videos.
Hopefully by now you’re getting the hang of the timeline. We’ve seen nearly every aspect of timeline items, from displaying rich cards and bundles to creating menus and even attaching contacts. Attachments are the last remaining piece, and are our first foray into dealing with binary (non-JSON) data.