Cell biology, also known as cytology, is a biology branch focused on studying cells' structure, function, and behavior, recognizing them as life's fundamental units. It explores both prokaryotic and eukaryotic cells, delving into topics like cell metabolism, communication, cycle, biochemistry, and composition. Utilizing microscopy, cell culture, and fractionation techniques, researchers uncover insights into cellular functions, crucial for understanding organisms. This knowledge proves fundamental across biological sciences and is integral to biomedical research, particularly in fields like cancer and genetics, where cell biology intersects with molecular biology, medical microbiology, immunology, and cytochemistry.history of cellsCells were initially observed in 17th-century Europe following the invention of the compound microscope. In 1665, Robert Hooke coined the term cells to describe the basic units of living organisms after examining cork; however, his observations were of dead cells, offering limited insights. Anton Van Leeuwenhoek, in 1674, marked the first analysis of live cells while studying algae. The cell theory, asserting that all living things consist of cells, emerged in 1838 through Matthias Schleiden and Theodor Schwann's observations of live plant and animal cells. Rudolf Virchow later expanded the theory, stating that cells originate from pre-existing cells. Viruses, lacking living cell characteristics, are studied in virology rather than cell biology.CLASSIFICATIONS OF CELLThere are two fundamental classifications of cells: prokaryotic and eukaryotic. Prokaryotic cells are distinguished from eukaryotic cells by the absence of a cell nucleus or other membrane-bound organelle. Prokaryotic cells are much smaller than eukaryotic cells, making them the smallest form of life.Prokaryotic cells include Bacteria and Archaea, and lack an enclosed cell nucleus. Eukaryotic cells are found in plants, animals, fungi, and protists. They range from 10 to 100 μm in diameter, and their DNA is contained within a membrane-bound nucleus. Eukaryotes are organisms containing eukaryotic cells. The four eukaryotic kingdoms are Animalia, Plantae, Fungi, and Protista.