A fatty streak is the first grossly visible (visible to the naked eye) 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 beneath[ambiguous] the inner, endothelial layer of an artery. Fatty streaks may also include T cells, aggregated platelets, and smooth muscle cells. It is the precursor lesion of atheromas that may become atheromatous plaques. The phenotype is thoracic aortic fatty streak (EFO_0005617). Also known as: thoracic aorta fatty streaks, thoracic aortic fatty streaks.