Students' Laughing

My favorite time in the classroom is when students are laughing. I don't necessarily mean laughing at my jokes (though I appreciate a polite chuckle here or there), but just genuinely laughing as they work. I see it sometimes when they are working together. One student makes a a funny comment and the others starts to chuckle or sometimes they poke each other in jest. I walk around the classroom watching them and say to myself, "this is how I want it to stay."