 There are three stages in the interface. So when a cell is just doing its thing and it doesn't look like it's actually dividing, it can be in one of three different stages of interface. These stages are functional stages as opposed to structural. Like we can't actually look in and see the difference from a microscopic view. We probably could see the difference if we could dive in with an electronic microscope and do some kind of crazy magic school bus evaluation, but we're not going to do that. So we can't actually tell the difference between these stages anatomically, but there are functional differences. So back in the day, they thought that nothing was happening during interface. This is a common perception that happens where literally many, many times we've looked at a process and gone, ah, nothing's going on there. So let's name it nothing. And G actually stands for gap. So this is actually considered the first gap where nothing is happening. But really during G1 of interface, which is the first stage of interface, the cell is living. I say chilling like a villain because that's way cooler than just living. But it's doing its thing. So if it's a muscle cell, it's just contracting. If it's a neuron, then it's sending messages. And if it's an endocrine cell, it's barfing out hormones. It's just doing what it's supposed to be doing to survive. At some point in G1, the cell may or may not get a message. It's time to divide. If you think about it, so this is optional. Now, this is a cool phenomenon. The cells lining your intestinal tract go through mitosis. They divide and replace themselves every 12 days. Every 12 days, you have a whole new lining of your digestive tract. What? That's crazy. That's like, that's really, really, really fast mitosis. So for those cells, G1 is going to be like not very long. Before the message is, dude, it's time to divide. For a cell like a neuron, some cells, some neurons, some cell neurons, but some neurons literally never get this message. And if they never get this message, they're considered to be in G, that's a zero, but they call it G0. And that means it's just going to chill forever. It's never going to get this message. So that message never gets sent. The chilling cell will chill for forever. Most cells do get the message that, you know, it's time to divide. And then there's this chemical glory in which they get the message and now they proceed into a stage called S, which stands for synthesis. And in the S phase, synthesis phase, what do you think is happening? Just take a wild guess. DNA replication. At this point, we go from having one, one, my chromosomes go from looking like that after S to looking like, I mean before S, to looking like this after S. So this is S. Does that make sense to you? Of course, we get our sister chromatids. Before S, there's no sisters in this mix. And there's a little bit of sadness about that because everybody wants to have a sister. But after S, we get some sisters in the house. And then it's a really crowded party in there. We've doubled our DNA. We haven't doubled the number of chromosomes because remember sisters are joined at one centromere. But then we go into, again, the message like everything's cool. We keep going. We've doubled our DNA. We move into G2, the second gap. And this is where everything else, everything else is prepped for division. Simply meaning, dude, we're going to need mitochondria for each cell. We're going to need some ribosomes for each cell. We're going to need a new nucleolus in each cell. Endoplasmic reticulum, got to have some of that. Everything else gets prepared so that the division of the whole process can happen. Now we're ready. All the way through interphase. There are these little checkpoints that say, are you cool? Because if you look wonky at all, like you have too much DNA, too little DNA, some crazy mutation, you messed up when you were replicating. All the way through this, these little checkpoints that say, sorry, dude, you didn't make the cut. You don't get to divide. And that, I'm just going to show you what seriously. If anybody can understand that, I would be delighted. Like that's unbelievable. Cancer is mitosis gone bad. Mitosis gone crazy. It's mitosis, too much mitosis. I mean, would you have ever thought you could ever have too much mitosis? But you can, and that's cancer. You're going to form a tumor. You reproduce too much where you're not supposed to and then you get a bump because there's growing tissue there. They think that cancer is caused by the malfunctioning of proteins at one of these checkpoints. So it's a huge area of research. Like, dude, let's find it. Who can find it first? Because if you can fix the protein that's broken and re-regulate mitosis properly, the results are done. Take that little medicine that makes that protein work again and you're stoked. Like, you've got that under wraps. How cool is that? The process, now we're ready. Now we've got two sets of our chromosomes. We've doubled other stuff. Now we're ready to go through the process of mitosis. So let's do that. Let's see what that whole process looks like next.