La infanta Margarita Teresa con vestido azul

This portrait had a job to do. The girl is Margarita Teresa, daughter of Philip the Fourth of Spain, and Velázquez painted her in her blue dress in 1659 not as a keepsake but as a report. She was promised to her uncle, the Holy Roman Emperor Leopold, waiting in Vienna, and a run of these portraits was sent east so he could watch his young bride grow up from a distance. She was about eight here. It was one of the last things Velázquez painted before he died the next year, and you can see the shortcuts of a master, the silver and blue of the gown dissolving into loose strokes that only resolve into fabric when you step back. She reached Vienna and married Leopold in 1666, and the picture stayed in the imperial city, where it still hangs.