Stages of development

Period of development	Age range	Some typical characteristics:
Prenatal	Conception to birth	The 38-week period of gestation includes these stages: Zygote – At conception, the fertilized egg is a single cell organism. In weeks 1 and 2, rapid cell division is followed by attachment to the uterine wall. Embryo – During weeks 3 to 8, the embryo grows through rapid cell division to include three cell layers which will later become the body’s organs and systems. Fetus – for the remainder of the pregnancy there is rapid growth in overall size, and all organs and systems.
Infancy	Birth to 1 year old	At birth, the child is completely helpless. Through the first year, physical growth is rapid. Motor control and abilities increase (head control, sitting, crawling, pulling to stand). The newborn’s cries gradually develop into more varied forms of expression. The infant starts to understand language. Memory and attention abilities increase during the first year.
Toddlerhood	1 to 2 years old	Increased physical growth and large muscle development allows for walking (first “toddling”), then climbing, and running. Increased small muscle development means the toddler can start to be more independent, e.g., using a spoon. Communication (understanding and expression) improves quickly with tremendous gains in vocabulary. Self-awareness increases. Difficulty with emotional expression can lead to frustration/temper tantrums.
Preschool (early childhood)	3 to 6 years old	Physical growth starts to slow down compared to earlier years. Motor abilities increase. Movements are more coordinated and fluid. Preschoolers become increasingly able to do things for themselves, e.g., dressing, eating, toileting. During these years, communication abilities improve and by the end of the period most children can say and follow fairly complex sentences. Social/emotional advances mean preschoolers can start to negotiate conflicts with friends. Thinking tends to be egocentric – from their own perspective.
School age	6 to 12 years old	Strength, balance and agility increase, and motor and athletic abilities become fine-tuned. Thinking and problem solving improve as school age children start to use more logic and less egocentrism. Most children learn to read, write and meet the expectations in school. For many children the influence of peers becomes increasingly important.