The final in-person showdown between Hillary Clinton and Donald Trump takes place on Wednesday night at the University of Nevada, Las Vegas. Here's what you need to know about the rules, format and structure of the third presidential debate:

TIME: The debate will begin at 9 p.m. ET on CNN and other major networks. It will last 90 minutes, with no commercials and no breaks.

MODERATOR: "Fox News Sunday" host Chris Wallace.

DEBATE FORMAT: The debate will be divided into six segments of 15 minutes each. The topics for those segments, selected by Wallace, are: "Debt and entitlements," "Immigration," "Economy," "Supreme Court," "Foreign hot spots" and "Fitness to be President."

SEGMENT FORMAT: Each segment will begin with a question. One candidate will have two minutes to respond, then the other candidate will have two minutes to respond. That will be followed by 10 to 11 minutes of open debate and discussion.

WHO GOES FIRST?: The first question will go to Clinton, according to the Commission on Presidential Debates. The same question will then be asked to Trump. In the second segment, the order will be reversed, with the lead-off question going to Trump, then Clinton. And so on.

PLACEMENT: As in the first debate, Trump will be on the left side of your screen and Clinton will be on the right, according to the Commission on Presidential Debates.