When the violin teacher asks your 5yo whether she can count in a foreign language (our family's native language, really), and the child hangs her head and says in shame: "yes, but only to 900".

Or when your 7-month-old baby boy lines up 5 baby food jars along the wall, crawls back a bit to inspect the formation, then makes adjustments so that the jars are equi-distant.

There are so many of such fun memories.