Gram’s stain [Hans C.J. Gram] , the method of staining microorganisms by using a violet stain, followed by an iodine solution; decolorizing with an alcohol or acetone solution; and counterstaining with safranin. The retention of either the violet color of the stain or the pink color of the counterstain serves as a primary means of identifying and classifying bacteria. Also called Gram’s method. See also gram-negative, gram-positive.
