The term gray matter refers to one of two components of the central nervous system (CNS). It is a type of neural tissue of the brain and spinal cord that, cut fresh appears pink or tan, fixed, appears darker compared to the other type, white matter, and in MRI sections can be darker gray or lighter gray than white matter depending on whether the image is T1 or T2 weighted and other factors.. Most gray matter is classified as an area of cortex or a nucleus. gray matter is composed predominantly of nerve and glial cell bodies ( Schiebler-1999 ). gray matter is found in all parts of the CNS of the human, macaque, rat, mouse, and other vertebrates ( Swanson-2004, Swanson-2015 ). Acronyms for gray matter structures or combinations of gray matter and white matter structures are three-letter combinations of capital letters followed by lower case letters representing substructures. relative location, and other features, e.g., AMGbl for basolateral nucleus of the amygdala. Final 28 Apr 2025.