The GRAM staining kit according to WEIGERT is specifically designed for the detection and differentiation of GRAM-positive and GRAM-negative bacteria. The versatility of this kit is demonstrated by its wide range of applications, from medical microbiology to water analysis. By combining several chemical reagents - including eosin, hematoxylin, LUGOL solution, carbolic-gentianaviolet solution and xylene-aniline oil - specific cell structures are stained differently. GRAM-positive bacteria show a black-brown staining, while GRAM-negative bacteria remain unstained. This allows precise categorization and identification of bacterial species, which is important for targeted therapeutic intervention. The result of a GRAM staining provides basic information about the morphology and cell wall structure of the bacteria under investigation, which is of high value for the understanding of infection processes and the selection of appropriate therapeutics.