During the preschool years, children experience significant physical and cognitive development. Their bodies grow stronger as muscle size increases and bones become sturdier. The brain grows rapidly, particularly areas related to motor skills, senses, and cognitive abilities. Major developmental milestones include gaining independence using the bathroom and developing hand preferences. Children's health risks include injuries, illnesses, nutrition issues like obesity, and extreme threats like abuse and neglect. Parents can support development by providing a healthy lifestyle, education on safety, and nurturing caregiving relationships.