Count the rings on a tree!
Did you know that someone who studies tree rings is called a Dendrochronologist?
When a tree is cut down you can see rings running through the trunk. These rings can tell you the story of the tree's life and how old the tree is.
Each ring represents one year so if you count them from the outside to the middle you can find out how old the tree is. Which ring represents your birthday? Or your Grandma or Granddad's birthday? If it was a big tree it could be over 100 years old!