Description:The U.S.'s top diplomat John Kerry kicked off his first day at his new job at the U.S. State Department on Monday (February 4) with a speech to employees who packed the building's lobby to welcome their new boss. Kerry said he has "big heels to fill" - a reference to his female predecessors, Hillary Clinton and Condoleezza Rice - in an address to State Department employees on the first day at his new job.(1:17)