Gram Crystal Violet, phenol free reagent is a component of BioGram Eco kit used for differential staining between Gram-positive and Gram-negative bacteria. Gram staining is a method of differentiating bacterial species and it is commonly known and used in microbiology. It is also one of the most frequently used diagnostic methods in hospital and clinical laboratories. Gram staining differentiates bacteria into two groups: Gram-positive and Gram-negative. Division is based on the two groups’ bacterial membrane structural differences, i.e. their capability of retaining the dye. BioGnost’s Gram Lugol solution, stabilized, which is an aqueous solution of iodine and potassium iodide in its composition, also contributes to this ability. During the Gram staining process, it allows the dye to enter the bacterial cell and create insoluble complexes of iodine and primary dye. With this action, it enables color retention and later identification of Gram-positive bacteria.