A woman with advanced cancer is offered enrollment in a clinical trial. The experimental treatment might save her life - or it might not work, and she would have spent precious remaining time as a research subject. The decision is impossible and essential. A parent considers enrolling their child in a trial of a new treatment for a rare disease. Standard treatments have failed. The trial offers hope but also uncertainty. A healthy volunteer participates in an early-phase drug study, contributing to science for modest compensation and the satisfaction of helping advance medicine.