an apparatus for holding liquid , such as a microtiter plate , in which a plurality of wells are formed . each of the wells have side walls that intersect in an edge that defines the boundary between adjacent wells . the edge boundary prevents liquid from collecting between the wells , thereby causing all of the liquid applied to the plate to enter one of the wells . the microtiter plate can be formed from a material having a reflectance and / or fluorescence that is optimized for the particular application in which the microtiter plate will be used . microtiter plates for use in fluorescence measurement applications are made from material having low fluorescence , such as a liquid crystal polymer , while microtiter plates for use in luminescence measurements are made from material having a high reflectance . microtiter plates for spectrophotometric applications are made with wells having clear bottoms and opaque walls . such clear bottomed wells can be made by incorporating a photobleachable dye into the plate material so as to render it essentially opaque and then irradiating the bottoms of the wells so as to render them transparent . such wells can also be made by forming the plate from an essentially transparent material and then irradiating the sidewalls with a beam of light so as to render them essentially opaque .