Upon injury, planarians can regenerate lost tissues. An intact, live planarian (left) had its tail amputated (dashed line). The tail fragment regenerated into a new planarian, shown at 1, 4 and 7 days post-amputation (dpa). The regenerating tail is labelled to show the nervous system and pharynx (also known as the feeding organ; yellow asterisk) (top) and the gut (middle), while the lower panel shows a merged image with the nervous system and pharynx in green, and the gut in purple. Scale bar: 200 μm. Adapted from Elliot et al. (2012).