But within this section, and within this section we have single strands that are exposed. And these single strands are commonly known as sticky ends. Why do we call them sticky ends? Well, because they're complementary with respect to one another. And if we somehow allow them to reconnect and then we use a special type of enzyme to reform these bonds right over here, these sticky ends, because they're complementary, they're going to stick right back together. Now, when scientists discover this, they realize that one important application of restriction enzymes will be to form recombinant DNA molecules.