Human thyroid parenchyma, light micrograph. The parenchyma is made up of numerous thyroid follicles of highly variable diameter, although large ones predominate. They gather in small groups, or lobules, separated by partitions of very loose connective tissue that appear as empty spaces due to tissue retraction. In the colloid, the usual artifacts of routine techniques such as retraction, breaks, and even detachment of the colloid are observed. The follicular epithelium is cubic or flat, as corresponds to large follicles.