To understand the friction between Russia and Ukraine, it's important to go back to 1991. Exactly 30 years ago this weekend, the Soviet Union formally dissolved and broke up into 15 separate nations.

Biden used to talk a lot about the COVID-19 death toll, but over the last year he's shifted to how fight the pandemic. Some want him to go back to addressing the country's grief.

Americans are scrambling to find out if they're COVID-free so they can go through with their plans. But for many, that means queuing up for hours or tracking down scarce at-home testing kits.

We spoke to four archaeologists of different specialties, who told us what they thought were some of the most important developments in their field in 2021.