The diverse forms of living organisms starting from microscopic unicellular organisms to giant multi cellular one’s have a common basic organization.

Even early philosophers and naturalist like Aristotle and Paracelsus could recognize this fact and concluded that all animals and plants are composed of few ‘elements’ which are repeated in them.

Lamarck observed, “Nobody can have life if its constituent parts are not formed of cell”. However, due to lack of proper optical device nobody could actually go further to establish the cellular organization of the body.

Discovery of Cell

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Discovery of cell was delayed till the development of microscopes with good resolving powers and magnification. Unaided human eye cannot resolve objects less than 100 micrometers apart. Many’ cells are too small to visualize with unaided eye. The first microscope was built by Zacharias Janssen and H. Janssen in 1590.

It was further modified with greater magnifying power by Galileo in 1610. However, it was a British mathematician and physicist Robert Hooke who in 1665 for the first time explored the microscopic world under a microscope developed by him.

He for the first time observed perforated and porous honey comb like structures in the remains of dead cells of a piece of cork (cork of Oak – Quercus suber). He coined the term cell for each empty honey comb like compartment (L. Cella-hollow space). His findings were published in a book “Micrographia” written by him. However, the term ‘cell’ is actually a misnomer as the living cell is neither hollow nor all the cells are covered by a wall.

Further studies of cells continued with the development of sophisticated microscope. In 1673 Lecuwen- hoek for the first time observed and described free living cells like some bacteria, protozoa, spermatozoa, RBC etc. Malpighi (1675) and Grew (1682) observed some plant cells. Further detailed studies of cells were interrupted till the invention of good compound microscopes, and better fixation techniques.

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In 1839 Czech Physiologist Johannes Purkinje observed dense complex fluid inside the cell called
protoplasm. Hugo Von Mohl (1846) confirmed this. Robert Brown (1831) found the presence of small spherical bodies within the epidermal cells of orchid root which were later known as nucleus.

In 1838 Schwann for the first time observed the cell membrane which was so named by Nageli and Cramer in 1855. It became clear that structurally a cell is a mass of protoplasm bounded by a cell membrane and having at its centre a spherical body, the nucleus.