A flow cytometer is versatile in its capability of measuring multiple parameters simultaneously These parameters include the physical properties of(e.g., cell size and cytoplasmic granularity), surface membrane, and nuclear antigens, and DNA-RNA contents of individual cells in a cell suspension. Surface, cytoplasmic, and nuclear antigens are detected by means of fluorochrome-conjugated antibodies. These antigens are thus the extrinsic properties of the cell. The physical properties of the cell are the intrin sic properties, because no exogenous reagents are added for their detection. These parameters are measured through an optical system, and the light signal thus generated is regis- tered in an electronic system. The computer system is responsible for data storage, gating, and graphic display on a screen