Breathing is a really cool thing. We breathe automatically without thinking about it, but we can also control our breath and play with it. We'll learn how our lungs work and why our bodies need this air in the first place. We'll also hear from a singer and a free diver about how they've trained their breath to do remarkable things -- and how you can too! And we'll talk to a doctor about how deep breathing can help you feel less stressed and she'll teach us an exercise you can do whenever anxiety starts to creep up. Plus: Our Moment of Um answers the question: what is the smallest unit of measurement?