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.
Many scientists have made discoveries relating to cell theory, but three scientists are usually given credit for its development: Matthias Schleiden, Theodor Schwann, and Rudolf Virchow. Together, these scientists put forth the three basic tenets of modern cell theory: All living things are made up of cells. Cells are the basic units of structure and function in living things. Living cells come only from other living cells. Early Discoveries. Cells were discovered long before cell theory was ...