The first cells ever named were already dead, seen in a slice of cork
Robert Hooke named cells in 1665 because the empty chambers in cork reminded him of monks' tiny rooms. What he saw were lifeless walls, revealing nothing of what cells contain. It took Anton van Leeuwenhoek, peering at algae in 1674, to watch living cells for the first time.
Cell biology, also called cytology, studies the structure, function and behaviour of cells, the basic units of every living organism. It covers both prokaryotic cells, which lack a nucleus, and eukaryotic ones, and it explores metabolism, communication between cells, the cell cycle and chemical make-up. Viruses fall outside it, since they lack the features of living cells; they belong to virology.
The field grew alongside the compound microscope in 17th-century Europe. After Hooke's Micrographia and Leeuwenhoek's observations, Robert Brown identified the nucleus in 1831. In 1838 the plant scientist Matthias Schleiden and the animal scientist Theodor Schwann concluded that all living things are built from cells, the functional and structural units of life. Nineteen years later Rudolf Virchow completed the cell theory by adding that every cell arises from the division of an existing one.
Modern tools go far beyond simple lenses. Cell culture grows large numbers of one cell type for studying ageing, testing drugs and toxins, and manufacturing vaccines and therapeutic proteins. Fluorescent tags such as GFP light up chosen structures, confocal microscopy stacks focused images into three dimensions, and transmission electron microscopy fires electrons through metal-stained samples. Cytometry sorts cells by size and content, while cell fractionation breaks cells apart and spins the pieces in a centrifuge so each can be studied separately.
The payoff reaches medicine directly. Understanding how cells work underpins research into cancer and many other diseases, and links cell biology with genetics, immunology and microbiology. Cytopathology diagnoses illness by examining loose cells or small tissue fragments rather than whole tissues. Its most familiar use is the Pap smear, which screens for cervical cancer and for precancerous changes that could lead to it.
Source: Cell biology
