If you see your science-loving neighbor headed home with a power cord, a handful of test tubes, a stopwatch, and a bag of potatoes, there’s probably no need to be alarmed. There’s a good chance he’s only conducting an experiment, a scientific test conducted under controlled conditions.
To refer to a scientific test, use the noun experiment. If you want to describe the work done in conducting such a test, experiment will do the trick as well, since it can also act as a verb, as in "scientists experiment with helium." You can also use it more generally to describe trying a new method or idea. For example, you could experiment with a new hairstyle or different routes to get to school or work.