Three-year-old boys wake up every morning and begin a search-and-uh-oh-I-need-to-be-rescued mission.

People my age were not designed to have one of these — it’s a privilege mostly reserved for the young and energetic, who can get onto and off of the floor without so much groaning, popping and creaking. But like medicine, in measured doses, it will cure whatever ails you.

Three-year-old boys are high-energy dynamos, dominoes waiting to be knocked over. They live life at 90 miles an hour and narrate every step. They devour reality, but seldom actually live in it. While you and I see them as small people, they see themselves as the largest, most powerful creatures on the planet.

They’re Iron Man, Captain America, Superman and Batman rolled into one. They can fly — just listen to the jet sounds — and when they run they make their own whooshing Ninja noises. There’s nothing they can’t climb, outrun or conquer. They learn something new every minute, and make up twice as much.

God built them close to the ground so that when they fall, it rarely results in injury. Although they sometimes cry — particularly if Mom’s around — for the most part they just inventory the boo-boos, pop back up and continue the mission.

If I fell, just once, the way ours falls 20 times a day, they’d take me to the ER, and from there to a nursing home.

Three-year-old boys eat a lot, and the feeding process leaves so much debris behind that you wonder if anything actually made its way into their digestive tract. Then they exercise their new-found ability to go to the bathroom and it’s confirmed that yes, some did. Quite a bit, actually.

Three-year-old boys bounce back and forth between inexpressible delight and unfathomable sorrow, sometimes only seconds apart. When you get down on the floor with them, delight kicks in. They will dash through the house and attack you from behind a hundred times in a row, and have no doubt that you’re really surprised, every time.

Wrestling is a sacrament, pillows are made to be tossed, and low pieces of furniture like chairs, couches, beds and tables are designed to be climbed upon and leapt off of.

Couch cushions, Mom’s purse, your toolbox, their toy box, food — it’s there to be deconstructed, unloaded, taken apart, examined, tasted, tossed. If you happen to have a soft bed, a trampoline or some other space you can safely toss a three-year-old into or onto, you can do that almost infinitely and he will never get tired of it.

But at three, more and more often, things seize their attention and hold it. The toy they’ve had for months suddenly becomes something else in their imagination and it’s the coolest thing ever. A book that was just an object to toss around is discovered to have actual writing and pictures. A stuffed animal gets a name, and a role, and becomes a constant companion.

Three-year-old boys are, above all, interactive. You read, sing and talk with them, not to them. They’re not interested in being entertained, but in entertaining. They don’t want to watch you do stuff, they want to help you. They want a job. They mimic you so perfectly it’s scary.

Three-year-old boys can get grouchy when they get tired, but if you promise them they can play in the bathtub — with rubber ducks and Miss Piggy and Elmo — they’ll gladly let you coax them into getting clean and ready for bed.

And if, by chance, you find that calm story about sleepy bears, and you read it often enough, and slowly enough, sometimes three-year-old boys will yawn a time or two and go right to sleep on your lap. Once they go, they’re gone, because they sleep just as hard as they play.

The only thing you can do at that point is rock them as long as you can, soaking up all the love, the joy, the energy, feeling the heat they’ve built up during the day dissipate into the atmosphere. Then you take them to their bed, kiss them on the cheek and bid them softly to have dreams as sweet as being awake was.

And you wonder who learned more that day, you or him.

Yeah. Everybody ought to have one of these.