Best Examples of Bringing an Audience Up to Speed in a Movie

I just finished watching Deepwater Horizon, which is generally fine, but one thing I really appreciated was the way it found to explain what was happening on Deepwater Horizon and what Marky Mark's company did, thus allowing the rest of the movie to be a lot easier to understand from both a technical and political perspective. Basically, an early scene has Marky Mark's young daughter practicing her speech for class on what her Dad does, with a Coke can as a demonstration.

That got me wondering, in an era where so many movies seem to just plunk two characters down and have them talk about things that they are both already aware of solely for the audience's benefit ("Wow, I can't believe it's been 5 years since you had that car accident where you lost your young son named Michael, after which your wife left you because she couldn't process her grief, and you moved back in with your estranged father...."), do you have any other examples where a movie found an elegant or effective way to deliver some complicated backstory or foundational knowledge required to understand the specifics of the story?