Color enhanced transmission electron micrograph (TEM) of thyroid follicles. Detail of simple cuboidal epithelium that lines the follicles and secretes hormones T3 and T4 (which are then stored in the colloidal center). Corners of 3 cells adjoin onto a fenestrated capillary containing red blood cells. This is a part of the blood supply which conducts hormones around the body. Magnification x4,000.