For thirty years, the NASA microgravity program has used space as a tool to study fundamental flow phenomena that are important to fields ranging from combustion science to biotechnology. This book assesses the past impact and current status of microgravity research programs in combustion, fluid dynamics, fundamental physics, and materials science and gives recommendations for promising topics of future research in each discipline. Guidance is given for setting priorities across disciplines by assessing each recommended topic in terms of the probability of its success and the magnitude of its potential impact on scientific knowledge and understanding; terrestrial applications and industry technology needs; and NASA technology needs. At NASA's request, the book also contains an examination of emerging research fields such as nanotechnology and biophysics, and makes recommendations regarding topics that might be suitable for integration into NASA's microgravity program.