How a child plays, learns, speaks, acts, and moves offers important clues about child development. Developmental milestones are things most children can do by a certain age. This series of checklists explains key milestones in several areas of development: social/emotional; language/communication; cognitive (learning, thinking, problem-solving); and movement/physical development. Checklists are available for children aged two, four, six, and nine months; one year; 18 months; and two, three, four, and five years. Each checklist includes a reminder to talk to your child’s doctor or nurse and request a developmental screening if you notice any of signs of possible developmental delay.