Sure, you know every Jay-Z album word for word, cover to cover. You're jokingly called the "hip-hop encyclopedia" in your circle of friends. You feel like you can decode any rap lyric without consulting Rap Genius. But when it comes to hip-hop, it's impossible to know it all. Even the most esteemed rap purist is missing out on a fact or two. For those born and raised in the '90s (and 2000s), especially, it's easy to gloss over the details of hip-hop's evolution. Consider this a much-needed history lesson for the next time that rap OG tries to son you.