 Okay. Did you have this exact list that I ended up with listing our levels of organization between the atom and the organism? One thing that I noticed that I did was I tried to put subatomic particles into this list when I was doing it while you were doing it just a minute ago. And then I remembered, oh no, I'm not including subatomic particles because those are smaller or less complex than the atom. We use subatomic particles to make up the atom. Just for the fun of it, let's just review really fast. What are the subatomic particles that make up an atom? Loud and proud, folks, loud and proud, shout it out, no matter where you are. Just kidding. You don't have to shout it if you don't want to. It's good to practice saying things out loud, especially when prompted to answer the question as long as you're not in a library and disrupting people. But the three subatomic particles we talked about that make up every atom are protons, positively charged particles found in the nucleus that determine the element that we're talking about, neutrons, neutrally charged particles that are also found in the nucleus and just contribute to the mass of an atom, and electrons, which are negatively charged tiny little particles that fly around the outside of an atom and are responsible for forming chemical bonds. We'll not directly consider any of those subatomic particles other than that we know they're what are used to build the atoms that we will consider in this lecture. Mostly our conversation about atoms is just going to be about the molecules that are built from those atoms, and the molecules that are built are actually pretty big, so we'll be talking about macromolecules, and so this part, I guess my whole point in bringing all of this up, is this part right here, the organelles and the cells. This is the purpose of the lecture. So we'll see these various levels of organization as we go into the content in this lecture. Right now, I want to provide us with some context, and so I want to remind us that well what we're talking about here are, if we start biggest, biggest perspective possible, we're talking about a human organism, and other critters do have the cells that we're going to look at, but we're just focusing in on what we know about humans. We're talking about cells of the integumentary system, so the skin, and the skin is actually an entire organ. I'm going to just write that down here, even though I didn't write down, integumentary system. Okay I did those at the same time or like piled on each other. The organ that we're dealing with is the skin. Our organs are many tissues working together to serve a common function. The function of skin, it's protective, it keeps the bad things out, it keeps the good things in. Thank goodness, it's like our bag that contains us. What would we be? Oh, I do not want to think about what we would be like if we didn't have skin. Your skin is made of three layers. I kind of think you might know this already. Do you? Let's just write them down. The epidermis is the outermost layer of the skin, so if you pat your skin, pat your skin, you're patting your epidermis. Your dermis is deep to that, and then you actually have another layer that I don't think we learn about that much called the hypodermis. And hypodermis, we're not, we're completely in this conversation, we're going to focus in on what's going on with the epidermis. The cells we're interested in, these melanocytes are found in the epidermis. But does this work for you that we're actually looking at many, many, many different kinds of tissues and structures working together to function as skin. And then I want to name the tissue that we're talking about as well. I told you that we were going to focus in on the epidermis. The epidermis is made of a special kind of tissue, and I'm going to name it for you loud and proud. It's kind of a long name, but I think it is worth being exposed to one of the many tissue types that if you go further in your study of human critters, and any critter, probably, this tissue type, you will see it frequently. So the tissue itself is called stratified squamous epithelial tissue. How's that for a mouthful? Stratified squamous epithelial tissue. I don't know. I feel like I'm doing a little aside into anatomy and physiology with this lecture, which is fun because it's like how you work. And that stratified squamous epithelial tissue, that's what you're touching. That's the epidermis of your skin. It's made out of that kind of tissue. Let's take a look. Here's how we take a look at the anatomy of our skin. And this is a chunk that, like, lovely. Thank you for taking a chunk out of the anatomy, taking a chunk out of the skin. You can see that we have hair follicles. We have all sorts of stuff. Do you feel like you can see layers here? Do you already have a sense of, oh, I see three layers. What were the three layers of our skin? The skin organ consists of the epidermis, the dermis, and the hypodermis. That is very messy handwriting, but it means hypodermis. I told you, where are we focusing our, where, what are we focusing on? Because we're not going to focus on the entire skin organ. We're going to focus in on our friend, the epidermis, which is this, you can see. Like it, it totally is separated, right? Like, structurally, you can see the place where the dermis changes. And now we are the epidermis. So this is our place that we're going to hang out and learn about the specific cells, including melanocytes that are found here. Okay, so you ready to go explore the cells of the epidermis? Okay.