1 A few types of cells are large enough to be seen by the unaided eye. The human egg (ovum) is the largest cell in the body, and can (just) be seen without the aid of a microscope. 2  Most cells are small for two main reasons:  The cellâs nucleus can only control a certain volume of active cytoplasm.
The atomic nucleus is the small, dense region consisting of protons and neutrons at the center of an atom, discovered in 1911 by Ernest Rutherford based on the 1909 GeigerâMarsden gold foil experiment.
The cell was first discovered by Robert Hooke in 1665 using a microscope. The first cell theory is credited to the work of Theodor Schwann and Matthias Jakob Schleiden in the 1830s.ver a century later, many debates about cells began amongst scientists. Most of these debates involved the nature of cellular regeneration, and the idea of cells as a fundamental unit of life. Cell theory was eventually formulated in 1838.