Updated on Nov. 25 at 5:30 p.m. ET

The Democratic-led House of Representatives is pursuing an impeachment inquiry into President Trump. Here is the key information you need in order to understand an increasingly complicated affair.

Read the latest news about the inquiry; listen to our special broadcast coverage.

First, some background: While momentum toward impeachment had been building among Democrats for months, House Speaker Nancy Pelosi, D-Calif., announced an inquiry in September — after a whistleblower complaint about a White House phone call with Ukraine. The House formalized the inquiry and outlined their path forward with a vote on Oct. 28. The first open hearing in the inquiry is scheduled for Nov. 13.

In a call with Ukrainian President Volodymyr Zelenskiy, Trump asked for an investigation into a debunked conspiracy theory about the 2016 election and into potential 2020 rival and former Vice President Joe Biden. The White House is also accused of withholding military aid to Ukraine for Trump's personal political gain. Trump maintains that he has done nothing wrong.

The White House has not released a full list of participants on the July 25 call, but NPR has compiled a list of people identified so far. Here's who they are.

Here's how we got to the impeachment inquiry, from Trump's early focus on Ukraine in 2017, to the release of the whistleblower complaint on Sept. 26. Read the timeline.

Since the original whistleblower complaint was released, the list of names of those connected to Trump's call with Zelenskiy or to broader Ukraine policy has grown substantially.

From the president to career diplomats to private lawyers, here is a quick guide to people connected to the events being investigated.

In-depth profiles and features: