Controlled in vitro studies of cells and tissues under the conditions of microgravity (simulated on Earth, or actual in space) can improve our understanding of gravity sensing, transduction, and responses in living cells and tissues. This paper discusses the scientific results and practical implications of three NASA-related biotechnology projects: ground and space studies of microgravity tissue engineering (JSC-Houston), and the development of the cell culture unit for use aboard the International Space Station (ARC-Ames).