The number of Western young women joining IS has increased in the last months. Most recently, three teenage girls from east London successfully travelled to Syria. They are now believed to reside in Raqqa. Who are these women, the so-called Jihadi brides, who want to join IS? And what drives them? What do we know of their role within IS? These are questions that need answering if we successfully want to tackle this new phenomenon. There is still much we do not know. In this Background Note, ICCT Research Fellows Prof. Dr. Edwin Bakker and Ms. Seran de Leede provide preliminary answers to these vital questions and explain what we know so far of these, often very young women.