When I first started work at the White House last January, there were countless reminders that I was in a whole new world. Whether the oversized hallways and doors of the Eisenhower Executive Office Building or your boss coming and going in a massive helicopter in his backyard, this was unlike any workplace I'd ever seen. One of those fixtures that always reinforces the honor of this place is the lone Marine standing outside the West Wing. I would come to learn that there are actually four Marines who rotate in half hour shifts, standing sentry whenever the President is in the West Wing. Learn more about these Marines -- and the source of their ambivalence towards Christmas trees -- in the latest "Inside the White House" video.