Researchers are using inexpensive components from ordinary liquid crystal display (LCD) projectors to control the brain and muscles of tiny organisms, including freely moving worms. Red, green and blue lights from a projector activate light-sensitive microbial proteins that are genetically engineered into the worms, allowing the researchers to switch neurons on and off like light bulbs and turn muscles on and off like engines.
Update: Also here:
Scientists have come a step closer to gaining complete control over a mind, even if that mind belongs to a creature the size of a grain of sand. A team at Harvard University has built a computerized system to manipulate worms—making them start and stop, giving them the sensation of being touched, and even prompting them to lay eggs, as seen in the video above—by stimulating their neurons individually with laser light, all while the worms swim freely in a petri dish
this link has a cool video