Neurotransmitter - Wikipedia
Until the early 20th century, scientists assumed that the majority of synaptic communication in the brain was electrical. However, through histological examinations by Ramón y Cajal, a 20 to 40 nm gap between neurons, known today as the synaptic cleft, was discovered.The presence of such a gap suggested communication via chemical messengers traversing the synaptic cleft, and in 1921 German ...