Hair Attack (IMAGE) Rockefeller University Caption Hair follicles cannot grow properly (bottom) when a type of skin cell called dermal papilla lacks the receptor that binds BMP, a signaling molecule that, when present, instructs stem cells to trigger hair follicles into action and make hair (top). Credit The Rockefeller University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.