Henri Tajfel grew up in Poland. He was studying in France at the outbreak of WWII, volunteered in the French Army, was captured by the Germans & made a prisoner-of-war. At the end of the war, he discovered that none of his immediate family had survived the Holocaust. This loss was central to his pursuit of the psychology of prejudice & intergroup relations. With John Turner he developed the incredibly influential Social Identity Theory. They proposed that identity is built on the basis of membership of ‘in-groups’ and enforcing boundaries with other ‘out-groups’. To this day his work influences prominent social psychologists such as Steven Riecher & Alex Haslam, as well as many areas of social psychology, including intergroup relations & organizational psychology.