Why do we kiss? And why does it make us feel so good? Find out in our latest online Science Forum discussion. We're discussing the science of kissing with Sheril Kirshenbaum, author of the new book "The Science of Kissing: What Our Lips Are Telling Us." Kirshenbaum recently spoke with the The World's science correspondent, Rhitu Chatterjee. Listen to that interview in the latest World Science Podcast. And join the online conversation with Kirshenbaum. Click here to add your questions