KINYOUN solution serves as a critical component of the Kinyoun cold staining method, a variant of Ziehl-Neelsen staining. This solution is used to detect mycobacteria, particularly Mycobacterium tuberculosis. The interaction of the basic fuchsin with the lipophilic cell wall of the mycobacteria stains them intensely red. The phenol in the solution acts as a staining enhancer and improves the binding of the dye to the mycobacteria. The addition of ethanol facilitates the diffusion of the dye into the cells. After application of the KINYOUN solution and subsequent counterstaining, mycobacteria become visible as red rods on a blue background. The KINYOUN solution is therefore essential for the diagnosis of tuberculosis and other diseases caused by mycobacteria in microscopic laboratory diagnostics.