Grocott (also known as GMS) is a special stain test performed by pathologists to look for fungal micro-organisms in a tissue sample. The most commonly identified fungal micro-organisms are Candida and Pneumocystis. GMS may also be used to look for some types of bacteria, such as Actinomyces and Nocardia. When a GMS-stained slide is examined under the microscope, these types of micro-organisms appear black while the background tissue appears green. This makes it easier for pathologists to see the micro-organisms, even when only a few are present in the sample.