Meet David Alexis, a 27-year-old musician and teacher from New York.
Alexis recently shared a heartwarming video on Twitter of him playing the piano and singing the O'Jays “Love Train” with an autistic man.
The tweet has received a lot of attention, with almost 4,000 likes and 3,000 retweets at the time of writing.
Alexis told BuzzFeed News: "I was surprised that the video was shared so many times around the world."
He said the clip was a segment of an hour-long music therapy session he does with adults with autism and people with intellectual and developmental disabilities.
People are seriously loving what Alexis does and have sent lots of words of encouragement his way.
Alexis said he sings songs that "generally have positive messages" for adults.
People are incredibly moved by the video.
As well as holding therapy sessions, the musician also teaches children in elementary school. And look how happy they are...
It's obvious why. He seems to be pretty much the best teacher ever.
"I believe in using contemporary music to appeal to music of students' everyday experience," Alexis said. "I use popular songs to introduce elements of music theory and production."