Regeneration science needs to broaden its focus to understand why some organisms can regenerate and others not.

When Science celebrated its 125th anniversary in 2005, the editors of the journal published a special issue in which they took a look at the most compelling questions faced by scientists. Among the top 25 questions was “what controls organ regeneration?” In the accompanying essay [1], Science argued that regenerative medicine will not be able to rebuild organs and tissues, unless researchers understand regeneration from a broad biological perspective – identifying the molecular and cellular signals that guide regeneration in regeneration-competent organisms, as well as those that prevent it in regenerationincompetent organisms, including humans.