A few years ago, TV celebrity Rachel Maddow was at Rockefeller University to hand out a prize that's given each year to a prominent female scientist. As Maddow entered the auditorium, someone overheard her say, "What is up with the dude wall?"

She was referring to a wall covered with portraits of scientists from the university who have won either a Nobel Prize or the Lasker Award, a major medical prize.

"One hundred percent of them are men. It's probably 30 headshots of 30 men. So it's imposing," says Leslie Vosshall, a neurobiologist with the university and the Howard Hughes Medical Institute.

Vosshall says Maddow's remark, and the word "dude wall," crystallized something that had been bothering her for years. As she travels around the country to give lectures and attend conferences at scientific institutions, she constantly encounters lobbies, conference rooms, passageways, and lecture halls that are decorated with portraits of white men.

"It just sends the message, every day when you walk by it, that science consists of old white men," says Vosshall. "I think every institution needs to go out into the hallway and ask, 'What kind of message are we sending with these oil portraits and dusty old photographs?'"