The double-tagged Quenchbody immunosensor becomes fluorescent when its target antigen—the nucleocapsid protein from SARS-CoV-2—binds at the antigen-binding region of the antibody fragments. This approach is fast, cost-effective, and convenient to use in practice, making it ideal for point-of-care testing as well as batch processing of patient samples. The above image, which illustrates how the immunosensor becomes fluorescent upon antigen binding, was selected as the back cover for Issue 22 of the Analyst journal.