India ink, also known as Indian ink or Chinese ink, is a traditional black ink that has been widely used in various artistic, writing, and laboratory applications. In the context of laboratory use, India ink is primarily employed as a staining agent for biological and histological preparations.

In laboratory settings, India ink is often used for the preparation of microscope slides and the visualization of structures and cells under a microscope. It is particularly useful for highlighting cell morphology, such as the outline and shape of cells or the presence of structures like nuclei or intracellular components.

India ink staining is commonly used in microbiology for the detection and identification of microorganisms, particularly fungal cells. It can also be used in cytopathology to visualize cellular components, such as mitochondria or inclusions.