Created from frog stem cells, the xenobots are less than a millimeter (0.04 inches) wide, and travel inside blood vessels. They can walk and swim, CNN reports, and they can work alone and in groups.

Wood frogs (Lithobates sylvaticus ... This includes puncturing blood vessels, cell dehydration (as water leaves the cells to form ice), and damage to cell internal structures and membranes.

The frog's diet consisted of pinhead-sized crickets ... but multiple bacteria and a few white and red blood cells were evident on the slide.