International Women's Day is celebrated around the world--sometimes with an official national holiday--on March 8. This year marks the 100th anniversary of the first widespread observance in 1911. Here's a slideshow of the 172 images currently found in the Smithsonian's Women in Science set on Flickr Commons. Click on any picture to be taken to more information about it. I've already shared some of their stories here, and I'll share more in the days remaining for my guest blogging stint, but meanwhile, Happy International Women's Day.