This is a portion of the height of science fiction, comparable to Star Wars. Star Wars is an epic and a classic, but there's a lot of black and white. Firefly is done in shades of gray. The primary example of this is that the main characters would be considered crooks by anybody who didn't know them well. They rob, steal, and, more often than not, kill, though not in the sense of murder, more in self-defense. But what it simmers down to is the fact that they're all "just folk", ordinary people trying to get by. There's shooting, stabbing, smashing, exploding, and torture. There's sex, booze, and foul language. But the thing is, none of it is gratuitous, it's all in context. There are powerful moral lessons in it, and it is something everybody should watch, though probably when they're at least 12, because a lot of the jokes don't make sense until you hit puberty... :)