Via Slashdot, I have learned of the world's first artificial animal -- a jellyfish made of plastic and rat heart cells. The benefits are surprising and unexpected.
This jellyfish like thing starts to "swim" when exposed to electric currents, just as hearts beat in time to electric currents. Put this thing in a tank of sugar water and attach a pacemaker, and you have the perfect environment for testing heart drugs.
Traditionally, heart drugs had to be tested by breeding rats with sick hearts, injecting some rats with the drug and some with a placebo (saline solution to make sure that results aren't just some weird side effect of injections in general), and noting their recovery or death. Then human clinical trials were required because rats don't respond quite the same as humans. (Doing the original testing with humans would be condemning some humans to die, which people won't put up with.) All of this was expensive and took a lot of time.
So instead, we could make a human heart cell jellyfish, put it in the tank, and expose it to drugs dissolved in the water. The effects of the drug become apparently relatively quickly, suggesting which drugs, if any, are good candidates for a successful clinical trial.
The rat version? Proof of concept.