Welcome to Cleavage 101, students.
Here, Samantha Barks shows us the right way to do a plunging neckline in this Valentino dress. The Les Misérables star's slinky black number opens up right below the chest leaving just a few inches of side boob exposed. It's daring, but still decent.
Sadly, Heidi Klum crossed that line between sexy and skanky in her Julien Macdonald dress. The Project Runway host's chevron print gold gown is gorgeous, but that neckline plunges just a little bit too low (who are we kidding? It's a lotta bit too low!).
So, for those taking notes at home, side boob = hot. Bottom of the boob = not.