NASA uploaded a pretty neat video about understanding gut bacteria. The video starts by stating there are 3 pounds of bacteria in the human gut. Wow! Dr. Fred Turek of Northwestern Universities Center for Sleep and Circadian Biology is studying that bacteria in astronauts on the International Space Station.

When Scott Kelly went to live in the orbital complex for a whole year, one of areas scientists were studying was the bacteria inside Kelly's gut and how they changed (or didn't) over the yearlong stay in microgravity.