Models of human disease are beneficial for medical research, but have limitations in predicting the way a drug will behave within the human body using data from non-human models because of inherent differences between species. Many medications produce unexpected outcomes in the clinical trial stage using human subjects, despite success in animal models and even 2-D cell culture models using human cells. The “Organs-on-Chips” approach to human physiology research aboard the International Space Station may lead to more reliable and predictable results for drug development and reduce the need for animal testing.