What is gram staining

Gram staining is a staining technique which helps to differentiate bacterial species into two large groups i.e. Gram-positive and Gram-negative. This technique is based on the chemical and physical properties of their cell walls. The bacteria are stained with dyes and other substances, rinsed clean, then stained again with another dye. Based on whether or not their cell wall retains the Gram stain, the bacteria are classified.