Skin, our largest organ, acts as a protective barrier against pathogens that try to invade our bodies while constantly monitoring for potential threats. In the skin's outermost layer, the epidermis, reside keratinocytes, cells that detect danger and actively orchestrate the body's immune response. How these cells perform this task in a localized manner and then communicate the message with the entire immune system had been a mystery, but now a team of researchers from China has uncovered the signaling pathway.