Dockery's glamorous chignon would no doubt get Lady Mary's seal of approval. To recreate the style:

1.Part hair down the center and knot at the nape of the neck. You can tie hair like a shoestring for the same curvy, braid-like effect. Secure with bobby pins.

2. Insert a gold clip (or any other hair accessory you're digging) and position it just above the knot for a formal, polished look.

The model proved an undone updo can look sophisticated when she paired this messy knot with a classic lace Valentino gown. To pull off this look:

1. Apply a mousse (like Ouai Soft Mousse, $28) to damp strands and scrunch hair as you blow dry. This creates that sexy, beachy texture every one wants (and an essential element to this style).

2. Once dry, pull back pieces and loosely pin them at the nape of the neck. Keep in mind these pieces don't need to be uniform at the back of the head. In fact, they look better all over the place.

3. Spritz a firm-hold hairspray (we like Tresemme Mega Firm Tres Two Freeze Hairspray, $5.99) to finish the look. See? The chic style took you all of five minutes.

Though Mulligan's hair has grown significantly since her Gatsby pixie, it was still barely shoulder-length when she wore this knotted updo. To copy Mulligan's short hair updo:

1.Start by blow-drying your mane straight to give this updo a clean look. (If you want some added shine like Mulligan's, apply a hair serum like OGX Coconut Miracle Oil Penetrating Oil, $8.99.)

2. Pull hair into two ponytails (one high, one low).

3. Coil sections of each ponytail towards the center and secure with bobby pins.

Here's a sharp, side-parted upgrade to your basic ponytail. To copy Mara's volumized updo on lob-length hair:

1. Apply a volumizing mousse like Leonor Greyl Mousse Au Lotus Volumatrice, $46, to damp hair before blowing it dry.

2. After you've combed the hair back into a low ponytail and wrapped a tiny section around the elastic, apply Moroccanoil Treatment, $15, and Moroccanoil Glimmer Shine Spray, $28, to add dramatic shine and finish the look.

Scarlett Johansson is pretty much the queen of sexy (I mean have you seen "Ghost in the Shell"?), so you're guaranteed to catch a few glances copying this short updo:

1. You guessed it, start with wavy hair. You can achieve this with a blow-dryer diffuser or a 3/4-inch curling iron. Be sure to alternate directions if you use a curling iron to create more movement in the hair.

2. To give the style volume, back comb the hair at the middle of the head and work your way towards the crown.

3. Then, starting just above the ear, grab 2-inch sections of hair and twist. Pin these pieces at the back of the head. Continue this until you've pinned back all your hair on both sides.

4. To give the style sex appeal, finger comb your hair along the front hairline to free a few stray strands, and spritz the style with hairspray.