Salman Khan; Eric Greitens; Siddhartha Mukherjee; Paul Farmer

Salman Khan explains why the online learning channel, Khan Academy, has the potential to change the way we learn. Author and Navy SEAL Eric Greitens shares his new book, "The Heart and the Fist," about his service as a humanitarian and a fighter. Siddhartha Mukherjee, physician and Columbia professor, talks about "The Emperor of All Maladies: A Biography of Cancer." Harvard anthropologist and physician Paul Farmer shares his new book, "Haiti: After the Earthquake," and reflects on his work there.