Scientist. He was a pioneering bacteriologist who is best remembered for the development of the Gram stain. This was a method of staining used to distinguish and classify bacterial species into two large groups including gram-positive and gram-negative. Born in Copenhagen, Denmark, on September 13, 1853, he was the son of Louise Christian Roulund, and her husband, Frederik Terkel Julius Gram, a professor of jurisprudence (the study of law). He began his studies at the University of Copenhagen in Copenhagen, Denmark, under the guidance of famed zoologist and biologist Japetus Steenstrup, whose study of plants introduced him to the fundamentals of pharmacology and the use of the microscope. In 1878, he entered medical school and graduated in 1883. During this time he also traveled through Europe before settling in Berlin, Germany, in 1884. While in Berlin, he developed a method of distinguishing between two major classes of bacteria, this being the famous Gram stain technique which he was named. This particular method is still widely used in the standard procedures in medical microbiology today. In 1891, he began teaching pharmacology and was eventually appointed professor at the University of Copenhagen that same year. He later resigned his seat in pharmacology to become a full-time professor of medicine. His other work includes studying red blood cells in men and trying to recognize that macrocytes were characteristic of pernicious anaemia. He also published four volumes of clinical lectures, "Klinisk-therapeutiske Forelaesningerhat" (1902 to 1909), which are widely used in Denmark today. He retired from the University of Copenhagen in 1923. For his contributions to Danish medicine he was made honorary an member of the Svenska Läkaresällskapet (1905), Verein für Innere Medizin (1907), and Dansk Selskab for Intern Medicin (1932). Kristiana University (now University of Oslo) awarded him the M.D, honoris causa in 1912; and the Danish King awarded him the Dannebrog Commander's Cross, first-class (1912) and the Golden Medal of Merit (1924). He passed away in Copenhagen, Denmark, on November 14, 1938, at the age of 85, and he was buried in Assistens Cemetery in Copenhagen, Denmark.