And by circular, we simply mean it does not have a beginning and it doesn't have an end. Now, the plasmid is able to replicate by itself independently of that main genomes replication process. And the entire purpose of this plasmid is to basically contain these special genes that gives the cell special abilities. For example, these plasmids can contain genes that produce special toxins that protect the cell from other cells and other organisms. Or the plasma can contain these genes that give the cell resistance to antibiotics. Or these plasmids can contain special genes that code for special proteins, special enzymes that help the cell break down different types of products, as we'll see in just a moment.