Ever count the rings on a tree stump to find out how old it is? Well, turns out you can do that with corals too. You just need scuba gear, a pneumatic drill and specialized packing equipment that will keep a core sample alive until it can be put into a CT scanner that will visualize the bands.

The coral the scientists pictured here from the Woods Hole Oceanographic Institution (WHOI) are studying grows at about 1 - 2 cm per year. That means a growth three meters long could be nearly 300 years old.