Tension and fears are mounting
And here are some other pieces that break down what is happening:
The upheaval in Ukraine has spiraled into an increasingly tense dispute between Russia and the West.
The United States and many European countries are demanding that Moscow scale back its deployment of troops in Ukraine's southern region of Crimea. But Russian President Vladimir Putin so far appears unfazed by the pressure.
For a Russian invasion, it all feels very strange. The vibe on the ground in Crimea ebbs and flows from feeling like an eerie standoff to relaxed normalcy.
Crimea has become the flashpoint in a geopolitical crisis that's got London, Washington, the U.N. and NATO flustered. But so far, there isn't much of a dust up in the actual place where the troops invaded.
Russia approved the use of military force in Ukraine on Saturday, despite warnings of consequences from the West, and Ukraine responded by saying any invasion into its territory would be illegitimate.
The acting prime minister has gone so far as to say that a Russian invasion would mean war and an end to his country's relationship with Russia.
But there are so many questions as to how Ukraine arrived at this point: Why is Russia so interested in happenings there? Why does the West want to prevent Russian intervention? How did we get here? Why have thousands of protesters staked their lives, seemingly, on their desire for political change? And why has the government resisted their calls so vehemently?
Russia showed no signs of backing down Monday even as world leaders threatened sanctions and sternly rebuked the country for sending troops into Ukraine.
At an emergency U.N. Security Council meeting to discuss the unfolding crisis, Ukraine's envoy asked for help, saying that Russia had used planes, boats and helicopters to flood the Ukrainian peninsula of Crimea with 16,000 troops in the past week.
Putin was speaking to reporters Tuesday, harshly critical of Kiev's new leaders.
He called the parliament in Ukraine "partly legitimate" but said the country's acting president is not.