While Inauguration Day marks the transfer of power from one president to another, it also marks another major change at the White House: one first family moving out and another moving in.

This final piece of the transition happens behind closed doors, no cameras allowed.

The residence staff of the White House will be working furiously Monday on deadline to move the Bidens out and the Trumps in.

Gary Walters, the former White House chief usher for 21 years who attended five presidential move-in days, told ABC News the process is “organized chaos.”

According to Walters, the activity inside the White House is a well-organized ballet with “choreography that has to be minute-by-minute.”

Walters served seven presidents and first families at the White House, including during the Reagan, Clinton, and both Bush administrations.

“We have approximately five, five-and-a-half hours from the time they leave the North Portico until after the parade,” he said, emphasizing the short turnaround time.

“It’s somewhere in the vicinity of 110 people and they all have very specific jobs,” Walters added about the moving teams. “We also not only have the House, we have the West Wing and, specifically, the president’s Oval Office that gets transformed.”

Moving trucks are ready to go on the White House South Lawn driveway — empty ones moving away the outgoing family’s possessions, as well as ones loaded with the belongings of the incoming family.

The goal is to make the White House feel like home — or as homey as a 132-room mansion that is also a living museum of American history — can feel.

“Are you going to use pieces of furniture that you want to bring into the White House, or are you going to use furniture that is in our inventory, some of which may be there, some of which may be in storage?” Walters said, shedding light on the questions the staff must ponder.

The staff works frantically to make sure everything is just right when the first family walks into the White House for the first time.

“The aim of the residence staff is to have the president and the first lady move into their home when they come in from the Pennsylvania Avenue reviewing stand that their snacks are in the kitchen,” Walters said. “Their favorite items are where they expect them to be. There are no boxes unopened. They’re all open … It’s all set up beforehand. And when they walk in, they don’t see any unpacked boxes or extra storage items sitting around.”

Though this sounds like a wonderful perk of moving into the White House, Walters says this is also a practical reality because the president has to get to work on Day 1.

Amid the chaos, Walters says Inauguration Day can be emotional for the White House residence staff, especially those who have grown close to the outgoing first family.

“To get together with the president and the first lady is usually quite emotional because … family and the staff get to know each other pretty well,” Walters said.

During his time as chief usher, Walters would do something special for the outgoing president.

“I started a tradition of taking the flag that flew over the White House on the day they took office. And the flag that flew over the White House on the day that they were going to be leaving at midnight the night before,” Walters explained. “And we packaged those up in a box made of original White House wood from when the House was rebuilt in 1948, 1952.”

Walters then presented the flags to the presidents on the morning of their final day in office.