Twenty-one months is one of those ages that does not get talked about much because it falls in between the milestone checkpoints of 18 months and 2 years. But a lot is happening at 21 months and it is a genuinely fascinating stage to observe. Language is probably the most dramatic area of development at 21 months. Most toddlers at this age have somewhere between 20 and 50 words, and many are right in the middle of what is often called the vocabulary explosion. New words appearing almost daily. It is extraordinary to watch. Two-word combinations are starting to emerge or are just around the corner: more juice, daddy gone, big dog, no sleep. These early word combinations are a huge milestone. At 21 months, most toddlers are walking confidently, starting to run, attempting to climb everything, and beginning to kick a ball. Fine motor skills include stacking four or more blocks, scribbling with crayons, trying to use a spoon or fork with increasing success, and turning pages in books one at a time. Emotionally, 21 months is right in the heart of the toddler big feelings era. Your child understands so much more than they can express and that gap is a source of real frustration. Tantrums are normal. Emotional support and validation are more effective than trying to reason through a meltdown. Talk to your pediatrician at the upcoming 2-year check if your 21-month-old has fewer than 10 words, is not walking, or has lost skills they previously had.