Quick history lesson on beauty oils: These suddenly-seen-everywhere elixirs have been around since Cleopatra's days, and today movie stars from Marilyn Monroe to Gabrielle Union are rumored to have dabbed them on. But it wasn't until argan oil hit the scene about six years ago that they really exploded and proved to be a true miracle fix for everything from dry skin and frizzy strands to brittle nails. Today's ultra-refined (nongreasy!) formulas are often a blend of rich, hydrating botanical oils and can also be used in myriad ways, says N.Y.C. dermatologist Jeannette Graf. Click the photo to find out how to slip these essential oils into your routine.