Child psychologists at the University of London recently worked with the Grammy-winning singer Imogen Heap to create the perfect song to make babies happy.
They helped create four different melodies, and tested them on 26 kids to find out which one they liked most.
They did it by measuring their heart rates, and looking for cues like how much they smiled.
They also incorporated a bunch of sounds that babies responded to the most . . . like the word "boo" . . . the sound of a dog barking . . . and the sound of another baby laughing.
And they specifically wanted a female singer, since babies tend to like women's voices that sound like their mom.
Once they finished, they played it for 20 different babies, and it was a huge hit.
It's called "The Happy Song", and sounds like the kind of thing you'd hear on a kids show.
But it's the first song that's been scientifically engineered to make babies smile.