Elucidating the structure
In 1676 the Dutch microscopist Antony van Leeuwenhoek (1632–1723) published his observations of single-cell organisms, or "little animalcules" as he called them.
It is likely that Leeuwenhoek was the first person to observe a red blood cell and a sperm cell.
Henri Dutrochet (1776–1847) made the connection between plant cells and animal cells explicit, and he proposed that the cell was not just a structural but also a physiological unit: "It is clear that it constitutes the basic unit of the organized state; indeed, everything is ultimately derived from the cell" (Harris 1999, p. Dutrochet proposed that new cells arise from within old ones, a view that was echoed by his contemporary François Raspail (1794–1878).
Raspail was the first to state one of the two major tenets of cell theory: Omnis cellula e cellula, which means "Every cell is derived from another cell." However, despite this ringing and famous phrase, his proposed mechanism of cell generation was incorrect.
The open spaces Hooke observed were empty, but he and others suggested these spaces might be used for fluid transport in living plants.
He did not propose, and gave no indication that he believed, that these structures represented the basic unit of living organisms.
The first accurate description of the nucleolus was made in 1835.
Purkinje was the premiere cytologist of his day, and one of the most influential formulators of the cell theory.
He gave his name to structures throughout the body, including the Purkinje cells of the cerebellum.
Leeuwenhoek made numerous and detailed observations on his microorganisms, but more than one hundred years passed before a connection was made between the obviously cellular structure of these creatures and the existence of cells in animals or plants.
In 1824 Frenchman Henri Milne-Edwards suggested that the basic structure of all animal tissues was an array of "globules," though his insistence on uniform size for these globules puts into question the accuracy of his observations.
Marcello Malpighi (1628–1694), and Hooke's colleague, Nehemiah Grew (1641–1712), made detailed studies of plant cells and established the presence of cellular structures throughout the plant body.