Designer Michelle Smith was standing in the middle of a jean shop in the Marais neighborhood of Paris when her publicist called to tell her that Michelle Obama’s official portrait had been unveiled at the National Portrait Gallery and the former first lady was wearing Smith’s dress in the painting.

The dress has caused a stir not simply because it will be enshrined in history but also because it has such a central place in such a non-traditional portrait by artist Amy Sherald of a singular first lady.

The full-length dress is enveloping, but regal and reassuring.

The dress, Smith said by phone from Paris, is based on one that was in her spring 2017 Milly collection.

Although Smith offered Obama many iterations of the original dress, ultimately she chose the runway version with only a slight alteration.

“People have been describing the dress as couture, but the fabric is a stretch cotton poplin,” Smith says.

Part of the beauty of the dress is that it looks “Like couture but it’s made out of something spartan.”

The dress was chosen months ago, Smith says, and since she already had Obama’s measurements after having created things for her in the past, it was easy to work long-distance.

The choice of a Milly dress mimics, in some ways, Obama’s first significant fashion choice as first lady.