Tattoos have gained widespread popularity, with nearly one in three Americans having at least one. But beneath the colorful designs lurks a hidden journey. According to a new study, tattoo ink doesn’t stay in the skin; it travels and accumulates in the lymph nodes, potentially causing lifelong changes to the immune system. The findings offer no conclusion as to whether these changes are positive or negative, but suggest that pigment retention in lymph nodes can persistently alter local immunity.