This paper reports on research carried out through the EU FP7 Regenerative Medicine in Europe program. Drawing on both primary and secondary data, the paper examines the two main trajectories taken by stem cell innovation, one based on patient-specific therapies, the other more akin to the innovation path seen in the pharmaceutical sector. Each path raises distinct scientific, regulatory and commercial challenges and uncertainties for those involved. I analyze the implications of these two paths for our understandings of regenerative medicine and the innovation process more generally.