It arises from a one embryonic cell known as neuroblast

Types of neuron:
 According to number of process¬
(a) Unipolar: Only axon is there. e.g. mesencephalic nucleus.
(b)    Pseudounipolar: Only axon is there but it gets seperate to form dendron also." e.g. sensory ganglia.
(c)    Non-polar: Only cyton is there. e.g. Hydra and other cnidarians.
(d)    Bipolar: One axon and one dendron is there. e.g. retinal and cochlear ganglia.
(e)    Multipolar: One axon and various dendrons are there.

e.g. most of the neuron of the body.