http://www.slate.com/articles/video/video/2015/05/esa_video_tutorial_how_to_go_to_the_bathroom_in_space_video.html

Finally, after years of mystery and intrigue, we have the answer to a question asked since John Glenn and Friendship 7 first captured the world’s imagination. Thanks to European Space Agency astronaut Samantha Cristoforetti, we now know how one goes to the bathroom in space. And the answer is, basically: With a tube, a lot of suction, and a new appreciation for gravity.