Ukraine invasion: The history of tensions between Russia and Ukraine
Russia has launched an attack on Ukraine.
The two countries have a long complex history. Ukraine became independent in 1991, before then it was dominated by Russia.
Before the attack Russia made demands including a promise that Ukraine would not join Nato.
Nato is a group of countries which includes the US and the UK, which promises to defend each other if they are attacked.
Historically, Russia and countries that are a part of Nato have not always got on. Many people in Ukraine want the country to join Nato to avoid being dominated by Russia.
Ricky takes a look at the background to the attack.