Robots by the dozen are prohibitively expensive, so actually testing how large swarms would work together is often limited to computer simulations. That’s where Harvard’s Kilobots are beginning to bear fruit – at a cost of US$14 each in batches of a thousand, they’re a tenth the cost of their cheapest competitor. At such bargain-basement prices, Michael Rubenstein, Christian Ahler, and Radhika Nagpal at the Self-Organizing Systems Research Group have begun to build their own little robot army.