Naomi Watts' red carpet secret is well-fitting underwear.

'The Impossible' actress' stylist Jeanann Williams has spilled the beans on what makes the star look so good, saying she never lets her client attend a high profile event without stomach-controlling and cleavage-enhancing underwear.

She revealed: ''Undergarments, like Spanx, smooth everything out ... Silicone petals for the breasts. We use these all the time.''

Jeanann - who made The Hollywood Reporter's 25 Most Powerful Stylists of 2013 list - also explained she gets each outfit customised to fit Naomi's petite frame so she doesn't look swamped in dresses with long hemlines.

The stylist to the stars told People.com: ''You have to customize each look to make it work for your measurements and height.

''When dressing clients for the red carpet I always look at the runway image. If my client is 5'5″ [like Naomi], I know I'll need to take the hem up 4 inches.''

The 44-year-old actress favours a simple and sophisticated look, so Jeanann is conscious of keeping accessories minimal.

She added: ''If the dress is dazzling with jewels then go barely-there on the accessories and let the dress be the focus. Don't overdo it, over-the-top is no good.''