Paul Kalanithi was 36 years old when he was diagnosed with stage IV lung cancer. A Stanford neurosurgeon, Paul wrote the memoir, “When Breath Becomes Air,” in his final months of life. The book is at once a chronicle of surgical training and a search for meaning when the doctor becomes the patient. In an exclusive interview with Paul's wife Lucy, also a Stanford physician, Yahoo Global News Anchor Katie Couric discusses the book, family, and the search for meaning against the backdrop of cancer.