instrument (multi-mode plate reader). There are also instruments for measuring the dynamic or static light scattered from samples in a microplate. The range of applications for multi-mode plate readers is extremely large. Some of the most common assays are: ELISAs Protein and cell growth assays Protein:protein interactions Reporter assays Nucleic acid quantitation Molecular interactions Enzyme activity Cell toxicity, proliferation, and viability ATP quantification Immunoassays High throughput screening of compounds and targets in drug discovery Bead-Based Epitope Assay While "plate reader" usually refers to the devices described above, many variations are available. Some examples of other devices working with the microplate format are: ELISPOT plate readers, used to count the colored spots that are formed in the course of ELISPOT assays. High throughput imagers that can measure all the wells of a microplate at once High-content screening (HCS) systems that image each well with high resolution, to look at cell populations Label-free instruments that use specialized microplates to measure binding events without the use of chemical markers References Molecular biology laboratory equipment