Enlarge / Muscle atrophy is a known hazard of spending time on the International Space Station. (credit: NASA) Muscle-on-chip systems are three-dimensional human muscle cell bundles cultured on collagen scaffolds. A Stanford University research team sent some of these systems to the International Space Station to study the muscle atrophy commonly observed in astronauts. It turns out that space triggers processes in human muscles that eerily resemble something we know very well: getting old.