Other than grey matter, what else is the tissue of the central nervous system made of?

Areas of the central nervous system (CNS) that are mostly constituted of myelinated axons, also known as tracts, are referred to as white matter. White matter, which was previously assumed to be a passive tissue, influences learning and brain processes by altering the distribution of action potentials, serving as a relay and coordinating communication between various brain regions. White matter gets its name from the lipid concentration in myelin, which gives it a relatively light appearance. However, because myelin is primarily made up of lipid tissue veined with capillaries, the freshly cut brain tissue appears pinkish-white to the naked eye. Its typical preservation in formaldehyde is the cause of its white hue in prepared specimens.