Two parts of a neuron meet to form a synapse. The axon of a neuron that participates in the formation of a synapse is called a presynaptic neuron. Another neuron forming a synapse is called a postsynaptic neuron. There is a gap of about 20-30 nanometers between the synaptic knobs of two neurons. This gap is called a synaptic cleft. The synaptic knobs of both neurons contain neurotransmitters, neurofilaments and synaptic vesicles. These chemicals help in the transport of stimuli.