So restriction enzymes were essentially discovered and these biological molecules exist in bacterial cells and bacterial cells use these restriction enzymes to basically protect themselves from viral agents. So what these restriction enzymes do is they cleave DNA molecules or RNA molecules at specific locations at specific sites. And there are many different types of restriction enzymes also known as restriction and the nuclease that exist in nature. And so what that means is if we can extract and collect these restriction enzymes we basically have a very efficient way of cleaving our DNA molecules at specific locations. So, for instance, if we want to study the following DNA molecule we can cut it up into many small fragments by using restriction enzymes and then we can analyze and study and manipulate and amplify all these different types of fragments. In fact, we can use these fragments to essentially sequence DNA molecules and that leads us directly into factor number two.