This activity is designed to provide a visual demonstration of how the indirect enzyme-linked immunosorbent assay (ELISA) works. Four students play roles as either technician, washer, patient "A," or patient "B." Sponges are cut into appropriate shapes to represent various antigens and Y-shaped antibody molecules which contain variable regions complementary in shape to the antigens. Sponges are also used to represent the enzyme-labeled secondary antibody. As the drama unfolds, students should be able to visualize what is happening at the molecular level in the various wells of an ELISA plate (positive control, negative control, and experimental wells). It can also help students understand the ELISA in an educational setting where it cannot be carried out as a lab exercise because the necessary equipment or funds are not available.