Mini robots self-organise into army
No, it's not a sneak preview of an upcoming Doctor Who episode. The "Kilobots" might sound straight out of sci-fi, but this is real life. This is your future.
Scientists have actually created these obedient miniature robots that act together as a "swarm" to form a 1,000-strong army.
What do they look like?
Like tiny transistors on three spindly legs. Each robot is just a few centimetres across.
Each robot is equipped with infra-red sensors and two motors that cause their legs to vibrate.
And what can they do?
So far scientists have used them to make shapes, following simple orders such as "Form a star shape". They're also pretty good at forming into letters of the alphabet.
How do they do that? GPS?
Nope, not a Google Maps app in sight. It's all based on their location relative to one another.
After being given a command, the Kilobots begin to blink infra-red signals to each other and arrange themselves into the required shape.
The process begins with a tightly packed horde of Kilobots, programmed with a two-dimensional image of the desired shape and a set of fixed fixed rules they must follow.
Four "seed" robots start it all off, triggering a domino-effect of signals that spread through the rest of the swarm.
How each Kilobot positions itself depends on the distance between it and its neighbours. Robots become each other's reference points, building up an organised system from local interactions.
Where's the inspiration from?
Besides Hollywood? Nature, mostly. There's a load of creatures that evolved to do a similar thing millions of years before humans even thought about it.
Starlings flock together in cloud-like "murmurations".
Single-celled amoebas join together to create a "fruiting body" when food is scarce, while
The co-ordinated colour changes of individual cells in cuttlefish help them to blend in with their surroundings.
Army ants link their bodies to form rafts and bridges that help them cross difficult terrain.
"The beauty of biological systems is that they are elegantly simple - and yet, in large numbers, accomplish the seemingly impossible," explained Professor Radhika Nagpal, from the Harvard School of Engineering and applied Sciences (HEAS).
"At some level you no longer even see the individuals; you just see the collective as an entity to itself."
What do the scientists say?
Well, they're very excited. Apparently this is the kind of technology that's going to dominate our future.
Professor Nagpal said: "Increasingly, we're going to see large numbers of robots working together, whether its hundreds of robots co-operating to achieve environmental clean up or a quick disaster response, or millions of self-driving cars on our highways. Understanding how to design 'good' systems at that scale will be critical."