The first major museum exhibition to address gender and sexual identity: Hide/Seek: Difference and Desire in American Portraiture, opened at the National Portrait Gallery today. The exhibit isn't overtly sexual, though — rather, it's sensual, subtle, and often sad. While some of the artists selected for the show were forthright about their sexuality, many were not, and they had to communicate their intentions through layers of subtext. Especially from the most closeted artists, there's much to decode.

The Thomas Eakins painting "Salutat" comes at a time when masculinity was championed in art. And while Eakins' boxer doesn't stray far from that theme, his portrait is notable for its elevation of the boxer's physique, rather than his skill. In the portrait, the crowd cheers for the boxer as he walks into the ring, and every man's eyes are on his body. In art, the male gaze is a centuries-old tradition — but almost always on a woman's body, instead.

"Salutat" by Thomas Eakins. Oil on canvas. 1898

Keith Haring, famous for his playful, street-inspired patterns and figures, died from complications related to AIDS in 1990, at age 31. This painting, "Unfinished Painting," was painted in 1989, and is a self-portrait. Haring knew that he would never have the time to complete all the work that he wanted to do.

"Unfinished Painting" by Keith Haring. Acrylic on canvas. 1989.

When Robert Rauschenberg passed away two years ago, the New York Times made note of his brief, early marriage, but tiptoed around his longtime relationship with another one of America's most influential artists: Jasper Johns. While much of the art that Johns and Rauschenberg made while together is considered their most iconic, co-curator David Ward said that the Portrait Gallery selected works from after their relationship ended. "Canto XIV," by Rauschenberg, is one of those — the work refers to the circle of hell in Dante's Inferno where sodomites are forced to run barefoot in hot sand.

"Canto XIV [From XXIV Drawings from Dante's Inferno]" by Robert Rauschenberg. Edition 202/300 Lithograph. 1959.

George Bellows' "River Front No. 1" is as much an analysis of social class as it is sexual identity. It depicts poor immigrants bathing in the river, but Bellows is not the only observer. While most of the carefree, nude men in the painting are there to cool down, check out the dandy gentleman in the bottom left. He's just there to watch.

"River Front No. 1" by George Bellows. Oil on canvas. 1915.

Robert Mapplethorpe was always known for pushing the boundaries of sexuality — his homoerotic photography was rejected by the Corcoran in 1989 — but he, too, fell victim to AIDS. In this 1988 self-portrait, Mapplethorpe presents a memento mori aggressively and defiantly, in order to transform the way that AIDS victims were stigmatized.

"Robert Mapplethorpe Self-Portrait" Gelatin silver print. 1988.