Jamie Price, the VFX supervisor on the new movie Downsizing, talks about how movies use tricks to make people look tiny, beginning in 1935 with the movie The Bride of Frankenstein. Back then, it wasn't a matter of putting it all on a computer. There have been many different techniques used between then and now.
You might be surprised at how many of your favorite movies did this, and you didn't even think about the work that went into the effect. That's the mark of a good special effect. Making it look effortless is a big part of the magic. -via Tastefully Offensive