A microtiter plate (spelled Microtiter is a registered trade name in the United States) or microplate or microwell plate or multiwell,[1] is a flat plate with multiple "wells" used as small test tubes. The microplate has become a standard tool in analytical research and clinical diagnostic testing laboratories. A very common usage is in the enzyme-linked immunosorbent assay (ELISA), the basis of most modern medical diagnostic testing in humans and animals.