MEMS (Micro Electromechanical Systems). Sometimes called
smart dust, they are dust sized particles, packed full of
sensors, lasers and communications transceivers, capable of communicating with one
another. They could be used for a range of applications from weather and pollution
monitoring to spying. In future, they could be small enough to remain suspended in air,
buoyed by the currents, sensing and communicating for hours. Currently the smallest
ones are about 5 mm long, solar powered.