 Okay, here's what I want you to know. I am trying to zoom out. I want to show you the visual of an epiphyseal plate so that you can imagine the process of interstitial bone growth that increases the length of a long bone. And it happens by the time you come out of your mama's belly, all you have left are epiphyseal plates, where interstitial bone growth can happen. Otherwise, all bone growth is oppositional. So by the time you are awesome like me, all of your endocon, like all of your epiphyseal plates have closed. And so there is no interstitial bone growth happening inside your body anymore because you're awesome like me. There are layers of, like there are places where we can identify the things that are happening in the process of interstitial bone growth at the epiphyseal plate, okay? Do you remember what did we have in order for bone to grow? We had to start out with a model. We had to start out with preexisting connective tissue. In the case, in this case, it's hyaline cartilage. So look, zoom in. Do you agree? Hyaline cartilage, look at the lacuna, the little space. Look at the cell inside. That's a little cartilage cell. That totally works. That's a little chondrocyte. You look at this tissue, you're like, it's pretty clear, it's nice, it's probably hyaline cartilage and you are correct. Now, we have zones. This area is the zone of resting cartilage. Here is my epiphyseal plate. Do you see how, like, what is going on here? There's something funky. Well, first of all, look. Look at how the cells, here the cells, the lacuni are big with a single cell inside and all of a sudden you end up with, like, these kind of stretched out long lacuni with lots of cells going on there. This is the zone of proliferation. This is where the cells are like, dude, something bad is going to happen, we better start multiplying. Then they start to hypertrophy. So here's proliferation, we're getting big. Hypertrophy, the lacuni get really big and the cells inside are really small. At the bottom of hypertrophy, you actually have the cells producing calcified cartilage matrix. And so they're pooping out cartilage at this point. That's the zone of calcification. Can't really tell the difference between hypertrophy and calcification but then we actually have the zone of ossification which is where the bone, the new bone is actually growing. All right, we're calling it good. We will see you in class. Bye-bye.