So sometimes you have enough points that when they all appear close together you can't really differentiate them. And leaflet has a pretty nice solution to this and that's to cluster them together and in a different resolution they'll break apart. So let's go through an example like this and I think you'll see immediately why it's useful. Okay, so let's just go through the code. Let's define a data frame with 500 latitude and longitude points that are kind of close together, okay? And then, I'm going to take my data frame, and pass it as the argument to leaflet. Then I'm going to pass the output of the leaflet evaluated at the data frame to the addTiles command. And then I'm going to pass the output of that to the add markers command and then it's just going to have default cluster options, okay. There we go and look at that. Now we see the cluster in it. It gives you the number of points in this cluster. So let's look at this big one. Actually, I want to do this 96 one since it's, see, there you go. It's right in the center of Baltimore. Look at that. Zowie! That's cool. Okay, see how they all bunch back together at different resolutions? There is all 500 of them, they're all in Baltimore. And as I zoom in, I could just do this forever. Okay, all right, now let's move onto the next thing. Since it's really quick I'm not going to really introduce it. Instead of adding clusters or standard pop-ups, you can add circles. And the way to do that is just add circles markers, see this command right here. Okay, so let's do the same thing. Here we're just going to do, A couple of 20 markers that we're going to add. And then we're just going to add circle markers. Okay, and there they are. And see now they look like little circles.