How we become individuals: Plasticity Hipothesis - Santiago Ramón y Cajal

Chemical synapses often have a remarkable capacity for short-term physiological changes (lasting hours) that increase or decrease the efectiveness of the synapse. Long-term changes (lasting days) can give rise to further physiological changes that lead to anatomical changes, including prunning of preexisting connections, and even growth of new connections.
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Chemical synapses can be modified functionally and anatomically during development and regeneration, and, most importantly, through experience and and learning.
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It is this potential for plasticity of the relatively stereotyped units of the nervous system that endows each of us with our individuality.