Everybody’s skin wrinkles with age, but the actual science behind why it happens is murkier than you may expect. Very few experiments involve validating theories with actual skin samples. The results clearly showed that as skin stretches one way, it also contracts in the other direction. “If you stretch Silly Putty for instance, it stretches horizontally, but it also shrinks in the other direction–it gets thinner. According to German, your skin’s mechanical properties get somewhat “wonky” as you age and “things degrade a bit.”“It turns out the skin stretches laterally more, which causes the actual wrinkles that form.