For instance, in our blood plasma, which is an example of an extracellular matrix, we'll find many different types of glycoproteins that play a variety of different roles. Now, how exactly does the process of protein glycosylation actually take place? This is what we're going to focus on in the remaining of this lecture. Now, oligosaccharides are basically very small polysaccharides that can have anywhere from three monosaccharides to, let's say, twelve monosaccharides. Now, oligosaccharides can be attached onto proteins and we attach them onto proteins via specific amino acids. So there are only three different amino acids that we can actually modify by covalently attaching these sugar molecules.