The growing recognition of stem cells as an important and exciting field will continue to draw investigators with diverse backgrounds-from biology, engineering, and the physical sciences-and thereby enable further progress in these and other new directions. This book discusses advances made during the last decade that have led to increasingly defined culture systems for growing stem cells, starting from co-culture with feeder cells in the presence of serum to growth on synthetic substrates in defined medium. In addition to highlighting many recent advances, it underscores the need for future work.