As thirty years have passed from the fall of the Berlin Wall, the article series “Solidarity” look at how the Polish solidarity movement changed the societal and political landscape of Poland. The movement grew out a labor movement in the 1980s into a national actors, which legacy is still visible in modern Poland. At the same time solidarity as a societal process and resources has become relevant in Europe and elsewhere in various contexts. Solidarity is often referred to in e.g. economic or social policy, in debating welfare states, immigration policy, or citizen activism. The article series delved deeper into these topics. The series has been edited by Sigrid Kaasik-Krogerus and Mikko Poutanen.