Description:Facebook COO Sheryl Sandberg discusses what inspired her to write her new book, 'Lean In,' and how working women can stop unintentionally holding themselves back both professionally and personally. She recalls a particularly troubling incident in which she spotted alarming phrases on t-shirts that were being sold at a major retailer. The shirts marketed to boys read, 'smart like daddy' while the shirts marketed to girls read, 'pretty like mommy.'(2:25)