Justin Trudeau is preparing to be sworn in as Canada's 23rd prime minister, but until then many Canadians may be wondering: who's running the country? Here's an overview of who's in charge, for now, and how the transition of power will take place.

Harper is prime minister until he resigns

Before Trudeau can be sworn in, Prime Minister Stephen Harper must indicate his "intention to resign" to the Governor General.

According to protocol, the Governor General then "decides who is in the best position to command the confidence of the House of Commons," which in this case is Trudeau, who won a majority of seats in the House.

Then, in a meeting at his official residence Rideau Hall, the governor general will invite Trudeau to form a government.

Once Trudeau accepts, a time and a date will be set for his swearing-in ceremony. The formal resignation of the outgoing prime minister is submitted to the governor general “very shortly” before the swearing-in of the new prime minister.

That’s why, prior to being officially sworn in, Trudeau is referred to as prime minister-designate rather than prime minister-elect, since the latter would suggest Canadians directly elect a PM.

Old government on 'Caretaker mode'

Former Canadian ambassador to the U.S. Derek Burney says that, until the prime minister-designate and the new government are sworn in, the old government remains in charge, but is operating in "caretaker mode."

"No major decisions will be taken without consultation with the incoming government," he told CTV’s Canada AM. "If there is an emergency, obviously that's the way matters will proceed. But by and large, we're in caretaker mode for the next two weeks."

Transition team

Behind the scenes, a team is already at work helping prepare for the transition, advising the incoming prime minister on his first key decisions, including how quickly to recall Parliament, making recommendations on size of the cabinet, and the hiring of senior staff.

Burney, who helped lead the Conservatives’ transition into power in 2006, said the incoming prime minister will be trying to build a team that has a "blend" of experience in government and public service.

"You also want a regional and gender dimension to the team to reflect the makeup of the electorate," he told CTV's Canada AM. "But the primary ingredients are: political people who are close to the leader, who understand the way he thinks, and people with experience in government."

Once the team is established, he said, it will be working from a "to do list" of main priorities for each day until the new government is sworn in.

Next, the team has to help the prime minister-designate select and vet his cabinet, before creating and distributing the mandate letters outlining incoming ministers' immediate responsibilities.

Burney said Trudeau will also be briefed extensively on pending issues and priorities, both domestic and international.

"The most immediate challenge for any new government is to set some priorities, because you can't do all the things you promised to do. But you've got to do a few of the things you've promised to do, and you got to get a sense of priorities right," he said.

This leads to the Speech from the Throne, where the new government has its first opportunity to lay out its priorities before Parliament.

Transition for new MPs

In addition to a new prime minister, 199 rookie MPs were elected on Monday night, 140 of them of the governing Liberal party.

Alice Funke, publisher of the website punditsguide.ca, said the new MPs are facing "intense" days as they pack up their campaign offices and prepare to head to Parliament Hill.

Once they arrive in Ottawa, each party will hold a caucus meeting for new and returning MPs, as well as outgoing MPs, she said.

She said outgoing MPs have 10 days to pack up their offices in Ottawa and their constituency offices, as well as settle any paperwork and financial payments.

"Then the new MPs will arrive and they'll all have one big meeting, and probably a big party or wake, or some combination thereof," Funke said.

New MPs will attend House of Commons training sessions advising them of their budgets, their new roles, and the resources that are available to them.

Funke said, many times when new MPs replace outgoing MPs, it's a very "collegial" handover, but not always.

"Sometimes, honestly, it's scorched Earth," she said. "You hope that the outgoing MPs will hand over the case files of the immigration cases, EI cases or tax cases that they're working on. Sometimes it doesn't work."