Stratigraphy, I have trouble saying these words, that's looking at the various layers of the Earth. And you might use some dating techniques, for example, potassium-argon, say, okay, this is that, a certain amount of age, that is a certain amount of age, these were maybe, this was volcanic rock from a volcanic eruption. And then you can look at the fossils. You could say, okay, a fossil that I found here is going to be newer than the stuff here, and it's gonna be older than the stuff here. This might be the newest of all. So you can look at relative dating, and if you're lucky enough to have some volcanic rock, you could do some of this potassium-argon dating. And there's many, many, many other techniques.