Recent scientific research has shown that the human brain develops almost from conception to perform basic biological and cognitive functions, process emotions and memories, think and learn, and understand signals from the surrounding world. On the journey from fetus to young adult, the structures of the brain are altered by experience, attachments, trauma, and learning. Today’s ever-more-sophisticated imaging tools generate a visual picture of all that, helping to decode the brain’s messages. How does a child’s brain change in response to events? When do markers of mental health problems become evident? Can brain abnormalities be detected and treated earlier in life?