Although three U.S. presidents have faced impeachment, none have been removed from office. Presidents Andrew Johnson and Bill Clinton were both impeached, but the Senate declined to remove them from office, and Richard Nixon stepped down before the House could vote.

How it works: Below is a graphic that explains the typical procedures for impeachment and removal from office.

A bill that would have allowed for the extradition of people from Hong Kong to China drove millions to the streets in protest in recent weeks and is the latest action blurring the lines of the “One Country, Two Systems” structure.

Why it matters: Hong Kong, a concession of the Opium Wars and former British colony, was returned to China in 1997 on the grounds that it would maintain significant autonomy for 50 years. A global financial center, Hong Kong’s economy was once more than 1/4 the size of all of mainland China’s. As China’s economy has ballooned, and its reliance on Hong Kong has diminished, Beijing has exerted greater influence. But attempts to erode Hong Kong’s autonomy have been met with repeated mass protests.

The Trump Organization's negotiations to build a tower in Moscow were a continuation of efforts that go back decades. Here's what we know, and still don't know, about the talks that continued well into the presidential campaign that landed Donald Trump in the White House.