The human brain develops to about 80% of its full capacity by age 3 and 90% by age 5. A newborn baby has all of the brain cells or neurons that they will have for the rest of their life. The connections between these cells, however, are what makes our brains function. Brain connections are what enable us to talk, move, think, communicate, and do just about anything that we are capable of doing. Infancy and the early childhood years are crucial times for making these connections. At least one million new neural connections, or synapses, are made every second, more than at any other time in our lives. This is A LOT of activity!!!