The ideal material for interfacing electronics with living tissue is soft, stretchable, and just as water-loving as the tissue itself--in short, a hydrogel. Semiconductors, the key materials for bioelectronics such as pacemakers, biosensors, and drug delivery devices, on the other hand, are rigid, brittle, and water-hating, impossible to dissolve in the way hydrogels have traditionally been built. Scientists have now solved this challenge that has long stymied researchers, reimagining the process of creating hydrogels to build a powerful semiconductor in hydrogel form. The result is a bluish gel that flutters like a sea jelly in water but retains the immense semiconductive ability needed to transmit information between living tissue and machine.