Longitudinal studies

Longitudinal studies are like keeping a diary of your life but for a really long time. You know how your parents take your picture every year to see how much you have grown? It's like that, but instead of just one thing, they watch lots of things, like how tall you are, how good you are at math, and what kind of things you like to do with your friends.

Scientists do this kind of study to see how people or things change over time. They might start following a group of people when they are babies, and keep checking in with them every year until they are really old. This can help them understand how things change over a long time.

It's like watching a tree grow. Imagine you see a little seedling and you want to know how it changes over time. You could watch it grow every day, and take notes on how tall it is, how many leaves it has, and how much sun and water it gets. That would be a longitudinal study of the tree!