Xenobots have been called the world's first "living robots". They are made entirely of living tissue, and can be programmed to move towards a certain object.
Once the subject of fantastical stories, nanoscience is now changing the world as we know it.
The smallest motors ever made could one day have a huge impact on our lives.
A single-atom engine is the latest example of how nano-technology can create machines to power tiny robots inside the body.