The average age for the start of puberty has been dropping for decades. It's a global trend that could be signaling a public health threat to the physical and psychological development of younger, more vulnerable swaths of the population. Still, there's no clear culprit for early puberty; it's a complicated puzzle with many scattered pieces. At the National Institute of Environmental Health Sciences (NIEHS), pediatric neuroendocrinologist Dr. Natalie Shaw has been assembling the pieces together and recently found a new lead hiding in plain sight.