Direct antibody recognition of supramolecular arrays of small molecules, rather than of an individual molecule, is demonstrated. Monoclonal antibodies, raised and selected against crystals of cholesterol monohydrate are shown by ELISA (enzyme-linked immunosorbent assay) and immunofluorescence imaging to specifically interact with monolayers of cholesterol at the air-water interface. This raises the possibility of producing antibodies against solid antigens and using them to tag geometrical arrays of molecules in, for example, membranes, which cannot be presented as such to the immune system.