You're looking at a tiny piece of glass, which is in fact a tiny camera that could provide any object with the means of capturing images. The small chip in it processes the incident light, and the sensor was developed by Rambus.

This sensor detects light passing through an etched surface and then uses some computing to reconstruct an image.

The results aren't perfect, but they're great given how small the sensor is. According to Rachel Metz from Technology Review:
Patrick Gill [from Rambus] is excited to show me a small, fuzzy-looking picture of the Mona Lisa, printed in black and white on a piece of paper. It's not much to look at, literally, but it's unmistakably her, with long dark hair and that mysterious smile.
[Rambus via Technology Review]