In this video, we're going to begin our introduction to the cytoskeleton, and so the cytoskeleton can be defined as a network of elongated proteins in the cytoplasm of a cell. And so, you can see that the root cyto in cytoskeleton correlates with the root cyto in cytoplasm. Now, the cytoskeleton of a cell actually has multiple diverse functions, and we'll get to talk about some of those diverse functions in our video here very shortly. Now, it is important to note that the cytoskeleton does have some resemblance to our own skeletons. And so, just like our skeletons provide our bodies with the shape and structure, and the skeleton also helps with movement because what would our movement be without our skeletons? Well, the cytoskeleton does something similar for the cells. And so, what you'll notice here is that some of the functions of the cytoskeleton include providing the cell with its cell shape, cell structure as well as providing movement for the cell, and it can also be involved with transportation in terms of transporting molecules within the cell, and it can also be important for biosignaling to help cells communicate with other cells and also for cells to be able to respond to their environments. And so, you can see how the cytoskeleton has many different diverse functions, and some of those functions including the shape, the structure, and the movement can correlate with our own skeleton. So that can make it somewhat easier for you to remember the functions of the cytoskeleton. And so, really there are 3 major components of the cytoskeleton that you should be familiar with, and notice that we have them numbered down below; 1, 2, 3, and so the very first component are going to be the microfilaments. And recall that the root micro is a root that means small, and in fact, this is important because microfilaments, they are going to be the smallest of the cytoskeleton components. So the microfilaments are the smallest in size, and usually, the microfilaments are going to be made of thin rods of repeating actin subunits. And so these, actin protein subunits are smaller components that come together in a repeating fashion in order to make up these microfilaments. And so if we take a look at our image down below of the cytoskeleton, you'll notice that we have a really cool micrograph of a bunch of cells on the left-hand side, and all of these different colors that you see represent the different components of the cytoskeleton. And again, there are 3 main components, and the first that we're talking about are the microfilaments which are shown on the far left here. And so notice that each of these red little circles represents actin proteins, actin subunits that again come together in a repeating fashion in order to make up the microfilaments which are going to be the smallest in size. Next, what we have are the intermediate filaments and the intermediate filaments, as their name implies, they are going to be intermediate in size. That means that they are not going to be the smallest in size and they are not going to be the largest in size. They are going to be in between the two. And also, these intermediate filaments can be made of variable proteins. So there are different proteins that can come together to make these intermediate filaments. And so if we look at our image down below, notice that the intermediate filaments are being shown here in blue. Now last but not least, what we have are the microtubules. Now you'll notice that microtubules also have this root micro, and so it's important to keep in mind that the microtubules are actually not the smallest in this case. Instead, the microtubules are going to be the largest, and so this micro root here can be somewhat misleading. However, what you can think of with the microtubules, you can focus on this tube part, and when you think of tubes like a water slide, you think of really large tubes, and so that can help remind you that the microtubules are actually going to be the largest in their size. And so the microtubules are the largest in size, and they form again these large cylindrical tubes that are made of repeating tubulin proteins. And so the tubulin proteins will come together in a repeating fashion in order to make up the microtubules. And so if we look at our image down below of these microtubules, notice that each of these little green circles that you see represents the tubulin protein subunits that come together in a repeating fashion to make this entire microtubule. And so, the interesting thing about the cytoskeleton is that it is very dynamic, meaning that it changes a lot all the time. These cytoskeleton components, all of them, can be spontaneously broken down and also spontaneously built together, so that they can change and be fitted to the cell's need at any particular time. And so, again, the cytoskeleton is going to function in many different ways, including cell shape, structure, movement, transportation, and biosignaling. And so, this concludes our brief introduction to the cytoskeleton and the 3 components: microfilaments, intermediate filaments, and microtubules, and we'll be able to get some practice applying these concepts moving forward. So I'll see you all in our next video.