The White House on Wednesday released a transcription memo of President Donald Trump's July phone call with Ukraine President Volodymyr Zelensky.
Trump asked Zelensky to "look into" former Vice President Joe Biden, currently the Democratic frontrunner in the 2020 presidential primary, and his son, Hunter.
The five-page memo, which is not a verbatim transcript. was publicly released a day after House Speaker Nancy Pelosi said the House of Representatives will launch a formal inquiry into whether President Donald Trump should be impeached.
The Democratic-controlled House will examine whether Trump sought Ukraine's help to smear Biden.
Here are some of the events that led to the impeachment inquiry.
Reuters contributed to this report.