The human brain starts developing in the first trimester of pregnancy and continues rapidly throughout childhood until adolescence and early adulthood. As the brain grows, it forms new connections within itself and sends signals to the rest of the body, transforming the little baby into an individual with skills that encompass multiple domains, such as how we move, use our hands to perform endless activities, how to interact with people, and how we solve problems occurring in our lives.

A child is said to have a developmental delay if they are unable to achieve developmental milestones by a certain age. The delay may be in one or more of the areas of gross or fine motor, communication, problem-solving, behavioural and social. This may arise due to various causes occurring at any stage in early life, such as heritable conditions like Fragile X or Down syndrome, premature birth, metabolic disorders or injury to the brain, autism, to name a few, as well as numerous environmental factors.