The third edition of The Neuron provides a comprehensive first course in the cell and molecular biology of nerve cells. The first part of the book covers the properties of the many newly discovered ion channels that have emerged through mapping of the genome. These channels shape the way a single neuron generates varied patterns of electrical activity. Next are covered the molecular mechanisms that convert electrical activity into the secretion of neurotransmitter hormones at synaptic junctions between neurons. The second part of the book covers the biochemical pathways that are linked to the action of neurotransmitters and that can alter the cellular properties of neurons or sensory cells which transduce information from the outside world into the electrical code used by neurons. The final section reviews our rapidly expanding knowledge of the molecular factors that induce an undifferentiated cell to become a neuron, and then guide it to form appropriate synaptic connections with its partners. This section also focuses on the role of ongoing experience and activity in shaping these connections, and finishes with an account of mechanisms thought to underlie the phenomena of learning and memory.