Dogs can smell cancer, Covid-19, and many other health problems in humans. Now, scientists are trying to duplicate these powers in robotic sniffers. But there’s a big challenge here: Scientists don’t really understand how smell works. This is the third episode of our six-part series, Making Sense, and it originally ran on March 10, 2021. For more, go to http://vox.com/unexplainable It’s a great place to view show transcripts and read more about the topics on our show. Also, email us! unexplainable@vox.com We read every email. Support Unexplainable by making a financial contribution to Vox! bit.ly/givepodcasts Learn more about your ad choices. Visit podcastchoices.com/adchoices