Publisher Summary This chapter describes the pinealocyte as a paraneuron and proves the usefulness of the paraneuron concept for answering questions in pineal research. Main representatives of the paraneuron family are, for example, (a) peptidergic hormoneproducing endocrine cells like the chromaffin cells of the adrenal medulla, parafollicular cells. of the thyroid, parathyroid cells, anterior pituitary cells, pancreatic islet cells, and basal granular cells in the gastro-intestinal tract, (b) sensory cells like the gustatory cells, hair cells of the inner ear and the lateral line organs, olfactory cells, photoreceptor cells of the retina, the pinealocytes, and liquorcontacting neurons, and (c) Merkel cells of the skin, melanocytes, and mast cells. All criteria characteristic of a paraneuron hold for the pinealocyte, but the same criteria are also properties of nerve cells. Naturally, there is no clear boundary between a neuron and a paraneuron. The distinction between a receptive region and an output region in paraneurons may help to explain morphological findings related to the location of end-feet of pinealocytes at the region of the basal lamina. Distinguishing between a receptive input, a conductive, and an output region in paraneurons may be useful in obtaining more information about this enigmatic cell organelle in mammalian pinealocytes.