It doesn't take long, either.
From the time the corn sprouts through the surface, it won't be long until it's knee high, then head high, and more.
As we drive by these fields it seems to happen overnight.
It's said, out here in the Midwest, that you can sometimes hear corn grow because it grows so fast. I don't know about that, and the linked article seems to cast doubt on it and some other agricultural myths.
The small couple of inches corn will continue to burst as the heat and humidity build it up toward the sky. (Maybe as high as an elephant's eye!)
The corn happens each year - but the same phenomenon happens around us all the time. Watch your kids or grandkids awhile and you will be convinced they grew up (height or maturity) overnight. That little one who was afraid of clowns is now graduating from college.
Yep, just like that. So, take a few moments to watch the corn (and your kids/grandkids) grow.
Harvest, and graduation, isn't too far off.