A worksheet function that is called by Excel can call back into Excel using the C API. An XLL command that is called by Excel can call the C API. DLL and XLL functions and commands that are called by VBA when VBA has itself been called by Excel can call the C API.
Cell Theory. The discovery of the cell was made possible by the invention of the microscope, which was made possible by improved lens-grinding techniques.Antoni van Leeuwenhoek (1632-1723), a Dutch tradesman, learned to grind lenses and assemble them into simple microscopes.nspired by Hooke's work, Leeuwenhoek began making microscopic examinations of his own. In 1678, he reported to the Royal Society that he had discovered little animals -- bacteria and protozoa -- in various samples. The society asked Hooke to confirm Leeuwenhoek's findings, and he did.
Quick Answer. In the 17th century, the English physicist Robert Hooke discovered plant cells while examining cork under a microscope. He was the first to refer to the units as cells because their boxy appearance reminded him of monastery cells. Robert Hooke, the Curator of Experiments for the Royal Society, performed extensive work with microscopes. He is also famous for discovering the law of elasticity, known as Hooke's Law, and for his book Micrographia in which he details his observations while using the microscope.