Our bodies, including our brains, are growing organisms, based on the DNA with which we were born. Like all other kinds of organisms, we humans begin with many variations on a basic body plan, including basic plans for each of our organ systems, including our brains..The subsequent growth and development of our many parts depends on our continuing daily experiences of chemical nutrition and of sensory information flow.

Like the first few years in the development of a tree, the first few years in the development of our brains and other parts of our bodies determines the main structures that we will live with and modify for the rest of our lives.

Just as it becomes difficult to modify the overall shape of the main limbs of a tree after they have grown, it becomes difficult to modify the main structures of our brains after they have grown. But we can continue to grow new "twigs" and "branches" in the hugely interconnected networks of our brains throughout our lives.