The crystal violet solution according to Hucker is a common staining solution in microbiological research. It consists of the basic dye crystal violet (also called gentian violet or hexamethylpararosaniline) and is primarily used for Gram staining, one of the most important staining methods in microbiology.

Gram staining allows bacteria to be divided into two major groups: Gram-positive and Gram-negative bacteria. In this process, crystal violet binds to the peptidoglycan layer of the bacterial cell wall and initially stains all cells purple. Subsequent treatment steps with Lugol's solution and alcohol then differentiate between Gram-positive and Gram-negative bacteria. Gram-positive bacteria retain the purple staining, while Gram-negative bacteria lose the purple staining and are stained red by counterstaining, often with safranin.

Hucker's crystal violet solution is a standardized and optimized solution for Gram staining and provides reliable and reproducible results. It is thus an indispensable tool for microbiological laboratories.