Hanno guardato la mia foto scattata quando ero ragazzo e si misero a ridere.

English Translation

They looked at the photo taken of me when I was a boy and laughed.

Is “si misero a ridere” very different from “hanno riso” or “risero” and how?


“Misero” is the passato remoto tense of mettere. “Si misero a ridere” literally means “they put (or set) themselves to laughing” but is translated as “they started laughing.”


“si misero a ridere” conveys the notion that they started laughing, probably continuing for a while.

That said, the sentence starts with the verb in the “passato prossimo” tense, and it should continue with the same tense (or both parts of the sentence should use the "passato remoto:

That is it should be either:
“Hanno guardato la foto e si sono messi a ridere” or
“Guardarono la foto e si misero a ridere”.