Adults may still be able to grow taller, as long as their epiphyses are not completely closed. To determine whether a person can grow taller or not, scientifically, the state of the epiphysis is determined by taking a bone age film to see if the epiphysis has closed, and then to determine whether there is a possibility of height growth. The general age of epiphyseal closure is around 20 years old. There are two factors that determine height, one is the genetic factor from parents. The other one is the acquired factors that promote bone growth. If you want to grow taller, you need to consume more calcium and high quality protein before your epiphyses close, and then you need to exercise more, get enough sleep, get more sunshine, and take enough vitamin D. All of these will help to improve or promote your height. If the epiphysis has already closed, then the hope of growing taller is not very big.