Harvard bioengineers have made an artificial jellyfish by growing a single layer of rat heart muscle on a patterned sheet of polydimethylsiloxane.  As you can see from the following video, when placed between two electrodes in water, this synthetic structure can swim exactly like its living counterpart. The rat muscle contacts when an electric field is applied across the structure, and then the elastic silicone pulls the jellyfish back to its original shape.

“Morphologically, we’ve built a jellyfish. Functionally, we’ve built a jellyfish. Genetically, this thing is a rat,” said Kit Parker, the researcher who led this project.

You can read more in Nature Biotechnology.