Have you had a birthday recently? Feeling old? Don’t worry—there’s a good chance that you’re younger than your infant self.
As an adult, you have billions more new cells and trillions of times more new molecules than you had in your body when you were born. Your body now has day-old cells, year-old cells, and only a relatively small proportion of decades-old cells (found in parts of your brain). Most of your body is much younger than the day you were born.