The camera modules used in today's smartphones are typically pretty small, as you can see from the image below. However if you look to the left, you'll see something even smaller that's set to be the future of spying.
Researchers at Rambus have developed a miniscule camera with a 200 micron (µm) sensor, which is smaller than the tip of a pencil. It's also completely lens-free, with the tiny sensor mapping out light signals before a processor compiles the data into a viewable image. (more)