Shorttitle: Our knowledge of human origins remains largely conjectural. The body is essentially a cellular structure, it begins its existence as a single cell, the fertilized ovum, it develops by multiplication & differentiation of cells, it matures as the cells & the substances they generate achieve their mature state;senescence is the decay & death the final cessation of cellular activities. Cell is the fundamental structural, and functional unit of living organisms. It contains the protoplasmic masses making up organised tissue, and nucleus surrounded by cytoplasm enclosed in a cell membrane. The Cell Cycle is that period of time between the birth of a cell, as a result of the division of it's parent cell & its own division to produce 2daughter cells. The present work throws light on "PROGRESSION OF CELL CYCLE,INTRACELLULAR CONTROL OF CELL-CYCLE EVENTS,RETINOBLASTOMA PROTEIN & CELL CYCLE CONTROL,EVOLVING IDEAS ABOUT CYCLINS."