Hemolysis is use in the empirical identification of microorganisms based on the ability of bacterial colonies grown on agar plates to break down red blood cells in the culture. When the organism has been grown on blood agar plates, it can be classified with regard to whether or not it has caused hemolysis in the red blood cells (RBCs) incorporated in the medium. This is of particular importance in the classification of streptococcal species. A substance that causes hemolysis is a hemolysin.