A fatty streak is the first grossly visible lesion in the development of atherosclerosis. It appears as an irregular yellow-white discoloration on the luminal surface of an artery. It consists of aggregates of foam cells, which are lipoprotein-loaded macrophages, located in the intima, the innermost layer of the artery, beneath the endothelial cells that layer the lumina through which blood flows. Fatty streaks may also include T cells, aggregated platelets, and smooth muscle cells. Although fatty streaks can develop into atheromas, not all are destined to become advanced lesions.