Experiments show that the fates of neural crest cells are not irreversibly fixed along a single pathway. One type of experiment involves the transplantation of neural crest cells from one part of the body to another. For example, in the trunk, many neural crest cells differentiate into norepinephrine-producing sympathetic neurons. Conversely, in the cranial region, neural crest cells give rise to acetylcholine-producing parasympathetic neurons. When thoracic neural crest cells are experimentally transplanted into the head, some cells differentiate into cholinergic parasympathetic neurons instead of the adrenergic sympathetic neurons normally produced. It works both ways, as cranial neural crest cells grafted into the thoracic region will form adrenergic sympathetic neurons.