08 July 2016
Vol 353, Issue 6295

About The Cover

Cover image expansion

COVER A robotic ray made up of rat heart cells, gold, and a polymer commonly used in breast implants. The robot ray mimics the form and function of a swimming stingray, but with a twist: Genetically altered rat cells allow the "creature" to sense and swim toward light. See pages 110 and 158. For more on the process behind the cover image, see
Photo: Ken Richardson