This chapter discusses cellular communication in the neural environment. The brain is composed of gray matter and white matter. The gray matter accounts for approximately 40% of the brain’s mass and comprises the neurons. The white matter accounts for 60% of the brain and is composed of various forms of glial cells. Neurons are embedded in a scaffolding of glia cells. Structurally, every neuron has four components: a cell body, a number of dendrites, an axon, and a group of axon terminations called presynaptic terminals. A neuron is like a battery and generates voltage. This voltage is known as the membrane potential. Neurons communicate with one another at highly specialized contact points called synapses. Most of the remarkable information-processing activities of the brain emerge from the signaling properties of synapses. This is mediated by the actions of chemical synapses, electrical synapses, and by the interactions of action and synaptic potentials.