On the 24th of February, Russian President Vladimir Putin ordered a military invasion of neighbouring Ukraine, triggering the largest refugee crisis in Europe since the Second World War. Almost 6 million Ukrainians have fled the country, half of whom have fled to next door Poland. During a week in April, Our World follows Warsaw's Mayor Rafal Trzaskowski - as well as refugees and volunteers living through the crisis. How have the people of Warsaw dealt with such a sudden increase in the city's population - and what is the long term plan for all the new arrivals?