This advancement could save the lives of an unreal number of rats. First consider that the European Union alone has about 30,000 chemicals whose lung toxicities need to be tested within the next decade. For each chemical about 200 rats are needed to test the effects of a single dose. If chronic exposure is to be tested on that chemical, about 3000 are needed. Not only would these microlungs save countless animal lives, but it could streamline the drug development process by skipping the animal testing phase and experimenting directly on human tissue.