Your stomach growls, asking to be fed; your aching muscles cry for a soak. But your skin is often not so easy to understand. It can be an elusive, emotional organ—reacting slowly or not at all at times, instantaneously or explosively at others—which might leave you wondering, "What on earth is my skin trying to say?"

"Invariably, patients tell me they wish they'd paid more attention to their skin," says Heidi Waldorf, MD, director of laser and cosmetic dermatology at Mount Sinai Medical Center in New York City. "They've ignored or misinterpreted its needs. Now all they know is that it's screaming, 'Help!' —and they have no idea where to begin."

Take a decade-by-decade look at some crucial and helpful information on your skin!