Take a good close look at Madame X's dress here. Or better yet, go the the Metropolitan Museum of Art in New York City and see the 7' x 3' version of the painting in all of its glory.
Madame X, aka Madame Virginie Amelie Avegno Gautreau, was a professional beauty of her day. Her reputation as such was built on her use of violet-colored powder and low-cut dresses, however when Sargent's famous portrait of her was exhibited at the Paris Salon in 1884, it caused a scandal. Evidently at that time it was acceptable to wear make-up (apparently the contrast between Madame's white face and her pink ear is a give-away), henna one's hair and wear revealing gowns (one chain strap was originally painted slipped off her shoulder!) as long as those activities weren't advertised in public, and in 1884, nothing advertised like the Paris Salon.
The portrait ruined the reputations of both Gautreau and Sargent, so naturally dressmakers and designers have been making copies of the scandalous garment (henceforth, the "X-dress") ever since. Linda Evangalista got to wear a near-exact copy of the X-dress for her August 2006 Vogue cover shot, without the corset, I'm sure, given her delicate condition. I'd like a X-dress in every color, even though color would probably take the edge off its X-like decadence. I shouldn't mess with perfection, should I?
A book was written about Sargent, Virginie, and The Scandal entitled: Strapless: John Singer Sargent and the Fall of Madame X. Dang, it's worth buying just for the title, isn't it?
**This October, a show entitled "Americans inParis: 1860-1900" opens at the Metropolitan Museum of Art. It will feature portraits by Sargent, including Virginie's, as well as paintings by Whistler and Mary Cassatt. Ooooooooh.