So let's suppose we have an individual who contracts HIV, and what that means is in their blood sample, in their blood, they're going to contain the antibodies against the antigen found in the HIV agent. So we can use indirect Eliza, for example, to test for the presence of the antibodies against that HIV agent. And that's exactly what we're going to use to demonstrate how this process actually works. So let's suppose we have a well, a container, and inside that well, so on the surface of that well, we essentially place the antigens that are found in the HIV agent. So the surface of the well is coated with a specific antigen that comes from that viral agent. And these antigens are shown in red.