Cell counting is rather straightforward and requires a counting chamber called a hemocytometer, a device invented by the 19th century French anatomist Louis-Charles Malassez to perform blood cell counts. A hemocytometer consists of a thick glass microscope slide with a grid of perpendicular lines etched in the middle. The grid has specified dimensions so that the area covered by the lines is known, which makes it possible to count the number of cells in a specific volume of solution.