<prompt> Gram stain is a?Simple stainDifferential stainNegative stainFluorescent stain  <response>: The Gram stain is the most impoant staining procedure in microbiology. It is used to differentiate between gram positive organisms and gram negative organisms. Hence, it is a differential stain. Gram negative and gram positive organisms are distinguished from each other by differences in their cell walls. Ref: Ananthanarayana panikers 9th edition 