The process that will ultimately give rise to the connectome begins about 25 days after conception, when the neural tube begins to form. By the end of the embryonic period (gestational week 10), the basics of the neural system are established. All the structures continue to develop throughout the fetal period and early childhood. By 6 years of age, the brain has reached 90% of its adult volume. By age 25, it typically is fully developed. Image: © TheVisualMD/Science Source.