The dendrites of a neuron are branching, tubelike extensions of the cell body that form a pattern resembling the limbs of a tree. Most neuron cell bodies have about six main dendrites, each of which is two or three times as thick as the axon of the cell. The distance between the cell body and the tips of the dendrites is about 0.5 millimetre. Dendrites are specialized structures for receiving impulses, mostly from the axon of another neuron. Dendrites and axons do not quite touch each other. In almost all cases, they are separated by an extremely narrow space called the synaptic cleft, over which nerve impulses are transmitted. These places where one neuron communicates with another are called synapses.