That little thing there is a temperature sensor. A very small one. One of the main reasons it's so small is the way it powers itself, doing away with the requirement for a battery by managing to suck enough energy to run out of radio waves beamed to it from a bespoke router.
A Dutch team at Eindhoven's University of Technology have built the thing, claiming that these wireless and battery-less sensors are the ideal foundation for a future Internet of Things home or office, where the sensors can sense forever and might be forgotten about rather than endlessly charged, plugged in and serviced.
The sensor is paired with a custom router than sends radio waves directly to the thing, with the maker claiming this makes it self sufficient enough to be installed under a layer of paint or plasterboard and forgotten about. It's built on 65-nm CMOS technology, with the maker hoping that they could be mass produced for a handful of pennies, should the Internet of Things ever turn out to be anything other than a flash in some too-expensive, Wi-Fi-enabled pan. [University of Technology via Engadget]