Chin Growth (IMAGE) University of Iowa Caption University of Iowa researchers find that we develop chins as our head size increases, from childhood to adulthood. At about 4 years of age (left), we have little indication of a chin, but by our 20s, we have a prominent point at the bottom of our faces. Credit Nathan Holton lab, University of Iowa Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.