In this video, I'm going to show you how to prepare a wet mouth slide of eukaryotic animal sounds, specifically epithelial sounds from the inside of the cheek. Hello! Let's put on our eye protection to start. Here are all the materials that I'll need to wet mouth my specimen, my microscope slide, and instead of using water, I'm going to be using a .9% sodium chloride solution. This solution is isotonic compared to the fluid inside the cells. If I used water, the cells would burst from osmotic pressure. Try to place a very small drop of the sodium chloride solution on the slide, because we'll be adding more fluid when we add the stain. I'm going to use a toothpick to obtain my specimen. I can get a good sample of epithelial cells simply by running that toothpick gently along the inside of my cheek. I place my sample on the slide simply by swirling the end of the toothpick around in the drop of sodium chloride solution. The used toothpick is a biohazard and must be disposed of properly. The stain I'm going to use is called methylene blue, cheek cells, epithelial cells are very transparent, and in order to see them under the scope, I'm going to need to stain them. Now that my sample is prepared, I need to put a cover slip over it, this clear square. The best way to apply the cover slip is to hold it at a right angle to the slide and then let it drop. This helps avoid the formation of air bubbles. Sometimes if you use too much liquid in your sample, when you drop that cover slip, the liquid can seep out the sides. I like to keep my slide nice and neat so I take a paper towel and blot up any excess. Remember that sample has cells in it so the paper towel will need to be treated as biohazard and disposed of properly. This is what my slide looks like when it's finished. Now I'm going to show you what these cheek cells look like when viewed through a compound light microscope. Here are my cheek cells at 100 total magnification. You see they look like little fried eggs and the blue dot inside them is the nucleus. They stick and clump together because they're sticky, they're cells of the mucus membrane. Here are the same cells, magnified 400 times their actual size. Here's a cheek cell viewed under oil immersion. That's at 1000 times its actual size. You can see bacteria that come from the mouth on and around that cheek cell, the little dots that you see in clumps on the cell and around the cell. Those are oral bacteria. More seriously nerdy, amazing free stuff at scienceproffonline.com.