Light microscopy of thyroid gland. The thyroid consists of thousands of thyroid follicles organised as epithelial cells enclosing a homogeneous core of colloid-type material (pink). Thyroid colloid comprises thyroglobulin protein which stores the thyroid hormones. Iodine from the diet is an essential component for the synthesis of thyroid hormones. The thyroid secretes its hormones into blood vessels by separating them from the thyroglobulin. Magnification x80 when height printed at 10 cm.