C Kerepesi

Inflammation is like the hand of a biological clock: the further it is pushed, the faster the body ages. Scientists have found a way to read that hand through chemical marks on DNA. They picked 127 genes that switch on during inflammation and learned to predict a person's age from their state. DNA methylation is a chemical mark that changes a gene's activity without changing the gene itself.

Picture biological age as a counter ticking away inside every cell. Sometimes it runs fast, sometimes it lags behind your passport age, and scientists have learned to read its numbers from chemical marks on DNA. Those marks are like pencil lines on a doorframe tracking a child's growth: from them you can tell how much the body has aged on the inside.