He's credited as being the "saving grace of New York fashion." He changed Louis Vuitton and turned it into the empire it is today. He was responsible for the infamous 1992 Perry Ellis grunge collection that people still talk about two decades later. Marc Jacobs, guys.

The designer, who is celebrating his 50th birthday today, is hardly a newcomer or an unknown. Quite the opposite, he's some kind of a celebrity in the fashion industry. His long career has included some downs (rehab and being fired from Perry Ellis, to name a couple) but also plenty of ups, much of which has been well documented by the media. You yourself might be well-versed in the life of MJ. But there might be a few bits of information that may have gone over your head. We're here to fill in the gaps. Here are not 10 or 15, but 40 Things You Didn't Know About Marc Jacobs.