Developmental milestones generally fall into four categories:

• Physical (movement and the use of large and small muscle groups; gross motor and fine motor skills, respectively)
• Social and emotional (how a child identifies and responds to their own and others’ feelings)
• Cognitive (a child’s ability to learn new skills and understand increasingly abstract concepts)
• Communication (language acquisition, verbal skills, and the ability to understand language)

Here’s a small sample of what milestones parents can expect at various stages of toddler development.

12 Months Old

Social and Emotional Development: At 1 year, your young toddler will begin to show more signs of social and emotional awareness. Your child may suddenly start to be “clingy” with certain people, often Mom and Dad, and act shy or nervous with strangers as well as cry when Mom and Dad leave. Your toddler should also begin to be delighted by playing simple games like patty cake or peek-a-boo.

Language Development: Your young toddler still won’t know how to say many words—most likely “mama” and “dada” as well as a handful of other words—but he should understand far more and be able to follow simple instructions. He’ll also try to imitate Mom and Dad.

Cognitive Development: It’s well known that toddlers at this age can be mischievous—it’s all a part of normal development. You’ll find that your toddler will explore his toys in new ways, throwing them or banging them to figure out how they work. You may also notice that out of sight no longer equals out of mind for your toddler, which unfortunately for Mom and Dad means no more simply hiding an item when you want a toddler to forget about it.

18 Months Old

Social and Emotional Development: Mommy and Daddy are likely still a toddler’s favorites at this age—and he’s probably showing a lot of affection toward the people who care for him. That also means your toddler continues to be clingy. “Stranger danger” is completely normal and developmentally appropriate at this age.

Language and Communication Development: Your child’s vocabulary should be expanding, and by 18 months, he might know up to a dozen words or more. In addition, by a year and a half, your child might be speaking in simple two-word sentences. Finally, expect your toddler to be able to point out what he wants.

Cognitive Development: Make-believe and pretend, while not fully developed yet, will begin to show up in your toddler’s play at a year and a half. For example, you may see your toddler pretend to feed a baby doll. Your child will also be able to identify objects by pointing, including parts of his body. And, your toddler should be able to follow simple directions, like “pick up the crayons.”

Movement and Physical Development: At 18 months old, toddlers are on the move, all the time. Your toddler should be walking on his own, and may even be running and going downstairs. He’ll also likely be able to help dress herself. And toddlers will begin to feed themselves with a spoon and should be drinking from a regular cup.

2 Years Old

Social and Emotional Development: Your toddler is continuing to become more social and independent. And, while they still won’t interact with other kids while playing, your child probably gets excited when other kids—of any age—are around. 2 year old also marks the beginning of tantrums for most kids who are learning how to express themselves when they are frustrated, upset, tired, or hungry.

Language and Communication Development: Your 2-year-old is now speaking in longer sentences—up to four words in some cases. That’s not surprising considering he knows up to 50 words and is likely learning new ones every single day. But you’ll need to start being careful of what you say: Your toddler is listening and will likely repeat you at inopportune times, which can make for some embarrassing situations.

Cognitive Development: Your toddler’s play is continuing to become more creative—you might see him making up stories or games to play. He’s also sorting items by shape and color and following more complicated directions that include two steps like, “Pick up your toys and put them in the basket.”

Movement and Physical Development: Running, climbing, throwing, kicking—your 2-year-old’s gross motor skills are on display on a regular basis. You can also expect your toddler to be able to hold a pencil or crayon and copy lines and circles.

3 Years Old

Social and Emotional Development: Younger toddlers don’t really play together—they engage in something called “parallel play,” which basically means that they are playing near each other, but not actually interacting with one another. This all changes at 3 year old. Moreover, your child is now forming his own relationships with his peers (you’ll probably hear all about his friends at school or daycare) and he’s learning how to navigate sharing, cooperation, and other socially acceptable behaviors.

Language and Communication Development: By this point, there’s a good chance you’ve lost count of the number of words your toddler says—and with good reason, your toddler’s vocabulary is probably a couple of hundred words, and he is happily carrying on conversations. Your toddler is also able to understand and follow more complicated directions with three or more steps (if he feels like being agreeable), and he’s beginning to understand more complicated language concepts like inside, on, below, etc.

Cognitive Development: Playing at three becomes far more creative—your child can do small puzzles, figure out how to make toys work on their own, play make-believe, build structures with blocks, and more. You’ll continue to see tantrums at this age, which often erupt as a response to a toddler not getting her way.

Movement and Physical Development: Your child has come a long way from “toddling” the shaky walk that defines the beginning of the toddler stage. As your child is on the cusp of aging out of toddlerhood, he’s running longer distances, climbing, and maybe even peddling a bike. Your child is also able to draw pictures, which may only be scribbles at this point, but he’ll likely be able to tell you a story about what he’s drawing.