Birth-to-Age-5 Timeline of Development

The Talaris Research Institute in Seattle has a fantastic research-based Timeline of Development that illustrates how children develop in the first five years. Milestones are organized into Social/Emotional, Cognitive, Language, Sensory, and Motor. You can click on each milestone to learn more about it, with links to reference texts; many of them link to Talaris Research Spotlights. You'll note that each milestone has a pretty wide age-range, and that it's usually more useful to focus on the sequence and tempo of developmental achievement rather than on comparisons with that precocious neighbor kid, or the cousin who didn't talk until he was 4 but went to Stanford.