They function as cutaneous nociceptors and are essentially used by vertebrates to detect noxious stimuli that often result in pain.

Free nerve endings have different rates of adaptation, stimulus modalities, and fiber types.

[1][2] Free nerve endings can detect temperature, mechanical stimuli (touch, pressure, stretch) or danger (nociception).

The term "free nerve endings" dates back to the 1890s, originally characterized by the absence of other cellular structures at their terminals.

Advances in non-optical imaging such as electron microscopy allowed for higher resolution examination of free nerve endings, enabling the finding that they are most often bundles of axons surrounded by a Remak bundle rather than truly unenclosed.