Despite the occasional controversy, the use of stem cells in science and medicine is increasingly important and widespread, and thus it is important to understand their basic characteristics, types, sources, and applications. This directed case study tells the story of “Carl,” a high school football player with an injured knee. His doctor recommends the use of stem cells in his recovery, and by reading their discussion, students acquire basic knowledge about stem cells that they then apply in a series of activities. The first activity has students choose a stem cell type and use PubMed and ClinicalTrials.gov to practice basic research skills. This is followed by a jigsaw activity that develops skills in peer-teaching and learning. Students then consider the options available to Carl and conclude the case by working on a “whodunit” scenario in which they must identify the kind of cells used in the treatment of another patient at the hospital. The case is ideally suited for introducing stem cell biology to students who have a basic background in biology, genetics, and cell biology.