There are usually three layers inside a blood vessel, the inner layer, the middle layer, and the outer layer. The inner layer usually has endothelial cells growing on the surface to protect the inner layer that is in contact with the blood. When the endothelium is damaged, there will be some oxidized lipid components in the blood, which will be easily deposited through the carotid artery with damaged endothelium, and over time, it will build up into a plaque. The main component of the plaque is what we call oil, which is the lipid component. Therefore, the formation of plaque in the left carotid artery is mainly the result of damaged endothelial cells, and the lipid is deposited on the surface of the damaged endothelial cells, forming a plaque in the long run, called left carotid plaque.