Curators have been studying Picasso's "The Blue Room"—one of the highlights of the artist's early 20th-century "blue period" —since 2008, and they've discovered it was painted over another work: a portrait of an unidentified man.

"The Blue Room" depicts a woman posing in Picasso's Paris studio, but underneath is a study of a mustachioed man in a bowtie. Researchers at Washington D.C.'s Phillips Collection revealed the hidden image with a combination of X-ray and infrared analysis.

"It's really one of those moments that really makes what you do special," Phillips conservator Patricia Favero told the AP. "The second reaction was, 'Well, who is it?' We're still working on answering that question."

Picasso reused many canvases early in his career, when he didn't always have the means to afford fresh ones. His paintings "La Vie" and "Woman Ironing" were both previously discovered to have been painted over other pieces.

[H/T NPR, Photos: AP Images]