Physicians, patients, and companies can now see the stem cell transplant business taking shape. Stem cell trials are finally in progress, allowing investors and corporate partners to finally see just how effective this multi-billion-dollar opportunity to replace many highly problematic organ transplants, and dramatically expand the procedures into new areas, can be. Beyond the lack of clinical conformation, stem cell transplantation therapy has been held back by the inability to culture large quantities of cells--as with whole organ transplants, there simply isn't enough tissue to go around. For the most part, companies have had to propose autologous transplantation strategies or, at best, transplants from one donor for just a few patients--an economically difficult-to-justify business. Geron, the only player in this group to have benefited from the last nine months of biotech stock mania, holds a key competitive advantage: its ability to use embryonic stem cells (ESCs) to create, theoretically, nearly infinite quantities of any cell in the body. But recent developments have stirred the competitive pot: a number of companies have created methods for growing enough adult stem cells to provide them to significant numbers of patients. Meanwhile, researchers have transformed fully committed adult stem cells into cells of different lineages, raising the possibility that alternatives to ESCs for tissue replacement or repair exist. The transplant replacement business--regenerative medicine--has caught the public's attention. Nonetheless, the stem cell industry has remained a start-up's trade, and it's easy to see why: large-company experiences in the area have not, for the most part, been happy ones, as companies face the issues of installing unpharma-like infrastructures to deliver personalized therapy, as well as ethical concerns, which must be given appropriate consideration. But these and other hurdles shouldn't obscure the growing opportunity. Stem cell therapy, so long a therapeutic chimera, now seems ripe for commercial exploitation.