The word cell is derived from the Latin word “cellula” which means “a little room”. It was the British botanist Robert Hooke who, in 1664, while examining a slice of bottle cork under his microscope (later named as compound microscope), found its structure resembling the box−like living quarters of the monks in a monastery, and coined the word “cells”.
Cell theory refers to the idea as cells are the basic unit of structure of life. Development of this theory during the mid 17th century was possible by advances in microscopy.
The theory states that new cells are produced from other existing cells, and the cell is a fundamental unit of structure, function and organization in all living organisms. Hooke's description of these cells which were actually non−living cell walls was published in his book called Micrographia. His cell observations gave no indication of the nucleus and other organelles found in most living cells.
Zacharias Jansen, was the first person to make a compound microscope while the first to witness a live cell under a microscope was Antonie van Leeuwenhoek. He described the algae Spirogyra as animalcules, which means“little animals”, and even observed bacteria.
In the year 1838, Matthias Schleiden, a German botanist, first proposed the idea that all plants consist of a large number of cells. In 1839, Theodor Schwann, another German zoologist, asserted that all plants and animals are made up of cells, which serve as the units of structure and function. This in short is called the cell theory. In 1885, Rudolf Virchow expressed that all cells arise from pre−existing cells.
Thus the classical cell theory states that all organisms are made up of one or more cells, the cell is the unit of structure and function of all living things, all cells develop from pre existing cells and every organism starts its life as a single cell.
Vital functions of an organism occur within cells, and all cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells. Each cell stores its own set of instructions for carrying out each of these activities. All cells are related by their descent from earlier cells.
Cells sense and respond to environmental fluctuations. Despite their individuality, however, cells in organisms also display a remarkable ability to join, communicate, and coordinate with other cells. The contraction of muscle cells moves our hands; when we try to lift an object, nerve cells will transmit that decision from our brain to the muscle cells of our hand. Everything an organism does occurs fundamentally at the cellular level.