So much of your child’s early life is marked by their developmental milestones: their first word, their first crawl, their first steps. It’s an exciting time: Babies and toddlers amaze us by picking up skills seemingly overnight. But it can also be a nerve-wracking time, as navigating the complicated world of healthy child development can be tricky. It can be hard to know when a missed milestone is indicative of a bigger problem, or if your kid is just a little late on the child growth and development timeline.

Babies’ brains prep for complicated tasks well before we observe their first steps or first words. Sleep, and the second stage of sleep in particular, play a key role in growth and development of kids at any age. For babies, sleep is when they encode all that they’ve heard and observed throughout the day. At one to two months, a baby should coo, cry, and grunt, and at six months, a baby should babble and recognize the sound of their mother and father. Talking to them in adult language throughout helps build their language skills. A first word should come around the 11 to 13 month mark. It’s important to know what the red flags are with speech delays — for example, if your child can’t say any actual words by 18 months, you should consult a specialist.

But development doesn’t stop in the baby years, and you’ll find information on growth and development during toddlerhood and beyond, when growth and development milestones become less obvious, and more about displaying the qualities of a mature person.

You’ll also find information on red flags. No two kids are the same: Each will pick up skills at different times. But remember: There’s never a downside to consulting a professional, even if you’ve only sensed one red flag or missed developmental milestone. Even if a developmental delay or condition like autism spectrum is diagnosed, early intervention is crucial in helping children adapt and thrive.