The first chromogenic culture medium (for detection of E. coli) was invented and patented by Dr. A. Rambach in 1979. The introduction of this medium triggered a revolution in microbial diagnosis driven by the introduction of a whole range of media for the detection of key clinical & food borne pathogens. The use of chromogenic culture media for the detection of bacteria is increasing steadily despite the introduction of other (often molecular biology based) techniques. What is chromogenic technology applied to culture media? It is colouring the developing bacterial colonies with distinctive colours in order to allow an easier differentiation of the growing micro-organism. Dr A. Rambach developed and patented the use, in microbiology, of a technology based on a soluble colourless molecule (called chromogen) which was composed of a substrate, targeting a specifc enzymatic activity and a chromophore. When the colourless chromogenic conjugate is cleaved by an enzyme of the target organism, the chromophore is released. In its unconjugated form the chromogen exhibits its distinctive colour and, due to reduced solubility, forms a precipitate. The result is a very specifc & distinctive colour-based differentiation, which is clearly distinguishable to the naked eye under normal lighting conditions.