In the first half of the last century, immigrating to Paris wasn’t rose-colored. Migrants arrived in a city that was growing polarized, xenophobic, nationalistic (sound familiar?). But despite overwhelming odds, incoming artists made their mark on the city. The Stedelijk Museum is showcasing more than 50 of them, starring Chagall, Picasso, and Mondrian. What would Paris have been without these lights? —E.C.