Landmark works of the 17th century concerning observations of blood cells are quoted in the article. „Simple“ and successively „compound“ microscopes made their appearance in the late 16th century and early 17th century. In 1656, Frenchman Pierre Borel, physician-in-ordinary to the King Louis XIV, who first applied the microscope to medicine described a type of „worm“ found in human blood. In 1657, Athanasius Kircher, a Jesuit priest and scientist from Germany, examined blood from plague victims, and described „worms“ of plague. In 1661, 1664 and 1665, the blood cells were discerned by Marcello Malpighi. In 1678, the red blood corpuscles was described by Jan Swammerdam of Amsterdam, a Dutch naturalist and physician. The first complete account of the red cells was made by Anthony van Leeuwenhoek of Delft in the last quarter of the 17th century.

        Key words: Blood cells - Discovery - History