Stacks at least two small objects (like blocks)

What is this milestone?

Hand-eye coordination and planning

Using careful hand-eye coordination, your toddler can balance one block or object directly on top of another without it immediately falling over.

Why it matters

Stacking requires precision, depth perception, and spatial awareness. It also introduces basic concepts of gravity, balance, and problem-solving as they figure out how to align the blocks.

What to expect leading up to it

At first, they will be much more interested in knocking down towers you build than building their own. Then they will tentatively try to balance two blocks, which requires them to learn the exact moment to release their grasp.

How to encourage and support it

Provide large, lightweight blocks (like chunky wooden blocks or large plastic bricks). Build towers together and cheer when they successfully add a piece. And yes, knocking them down is still half the fun!

When to talk to your doctor

The CDC's milestone checklists say what most children (75% or more) can do by each age. They list “Stacks at least two small objects, like blocks” by 15 months. If your child is not doing this by then, the CDC's advice is not to wait: talk with your child's doctor, share your concerns, and ask about developmental screening. The same goes at any age if your child loses a skill they once had, or if anything else about their development worries you. Source: the CDC's “Learn the Signs. Act Early.” milestone checklists, checked October 5, 2026.

CDC: Milestones by 15 months · CDC: all milestone checklists