Although his work as President of the United States officially begins on inauguration day, Donald Trump still has many more decisions to make in choosing his cabinet members.

A President’s cabinet is typically composed of a number of appointed people who generally head certain federal departments and give the President advice and counsel in his term. Because these jobs are crucial positions, they require Senate confirmation by simple majority.

Here are some of the key cabinet positions that Mr. Trump must fill and be approved before January 20th and some that are reportedly up for consideration:

Require Senate Confirmation

Secretary of State: Rex W. Tillerson – President and chief executive of Exxon Mobil, who is known to have ties with Russian President, Vladimir Putin. The main role of Secretary of State, a position previously filled by Trump’s election rival Hillary Clinton, is to execute non-military and non-homeland security aspects of foreign policy.

Treasury Secretary: Steven Mnuchin – Mnuchin served as Trump’s campaign finance manager and is known for being a former Goldman Sachs partner and hedge fund manager. The Treasury Secretary acts as head of the U.S. Treasury and is a principal economic advisor to the President.

Defense Secretary: James N. Mattis – A retired United States Marine Corps general, Mattis has already served as Commander of United States Central Command under Barack Obama from 2010-2013. The secretary of defense’s role is to exercise authority, direction, and control over the department of defense, as well as being the President’s main defense advisor.

Although Mr. Trump has many spots open in his cabinet to be confirmed and filled, there are a number of positions that don’t require Senate confirmation. Here are some of his already appointed cabinet members that we will see throughout his term:

Senate Confirmation Not Required

Chief of Staff: Reince Priebus – Priebus, an attorney, politician, and head of the Republican National Committee was appointed as Chief of Staff on November 13th, one of Mr. Trump’s first cabinet picks. The Chief of Staff is an important position as it manages the work and personnel of the West Wing, as well as helping the President’s personal agenda on administrative objectives.

Attorney General: Jeff Sessions – Sessions is the incumbent, or current, Senator of the state of Alabama. An avid supporter of Mr. Trump, Sessions was examined to be his possible running mate but Governor of Indiana Mike Pence was chosen. Unlike many of the candidates up for Mr. Trump’s cabinet, Sessions has experience in his appointed position as he served as Attorney General of Alabama from 1995 to 1997. The Attorney General of the U.S. is the nation’s top law enforcement official.

As January 20th comes near, much of the country is keeping a close eye on Mr. Trump’s potential cabinet members. How the President-elect will use his authority as one of the world’s most powerful men is reflected upon whom his closest advisors in his Cabinet are, making each position to be decided imperative.