Answer: Insulin

NASA has conducted numerous experiments in the microgravity of low-Earth orbit over the last thirty years with more than a few surprising results. Among those experiments, one discovery that potentially has the greatest good for the common man back down on Earth is that resulting from the production of insulin in microgravity.

Insulin, used to help diabetics regulate their blood sugar, has a crystalline structure. Insulin produced on Earth has an irregular structure and is prone to, on a microscopic level, folding and breaking under its own molecular weight. As such, large extended crystals were difficult (if not impossible) to produce on Earth, we had never been able to observe large and gravity-uninhibited crystals before. The insulin produced aboard the Space Shuttle Discovery in 1994 proved remarkable in several ways, including the clarity and size of the crystalline structure (which allowed scientists on Earth to study it with a clarity unavailable with terrestrial samples) as well as potency. The larger and more cleanly organized insulin crystals provided by the experiment proved to be incredibly effective compared to regular insulin samples; if the insulin could be mass produced on Earth with a matching structure, diabetics dosing down multiple times a day with insulin could instead dose down every few days.