Although most of the changes are too small to detect with the naked eye, everything you’ve experienced has altered the physical structure of your brain – from the expression of genes to the positions of molecules to the architecture of neurons. Your family of origin, your culture, your friends, your work, every movie you’ve watched, every conversation you’ve had – these have all left their footprints in your nervous system. These indelible, microscopic impressions accumulate to make you who you are, and to constrain who you can become.
