Method of forming a stain assessment target

A method of forming a stain assessment target for a biological material staining system comprises providing at least one region 11 of a substrate upon a support, such as a microscope slide 10. The substrate is formed from an optically transmissive material which is an analogue of biological tissue. A biological tissue sample 12 for inspection is also provided upon the support. The support, and the at least one region, together with the biological tissue sample are stained by applying at least one biological tissue stain under similar staining conditions. Preferably, the region(s) of substrate are provided in the form of a film, or may be deposited using a fluid jet printing process. A plurality of regions may be provided, each having a different thickness, or different stain absorption characteristics. The method may allow for images of tissue prepared using different imaging systems to be more readily compared.