Can you view someone's snapchat history?

Oh my gosh, I am SO worried about this Snapchat thing! My little one, they’re always on it. Are you telling me there’s a way to see what they’re actually saying? Not just who they’re snapping? Real messages? Like, the actual words?

Is it even legal? Because, you know, I don’t want to get in trouble, but I need to know what they’re doing! And will it show deleted stuff too? I’m practically sick with worry! Please, someone, tell me there’s a way to protect them! Are there apps for this? Are they safe? I’m desperate!