The "come back" of religion is subject to much public debate. While church membership and attendance in mainstream Christianity declines in Northern Europe, the evangelical movement thrives. With the arrival of migrant churches, Islamic groups and New Age, the religious field is diversified. All over the world, religious revival movements manifest themselves as major public players, often by making prolific use of the latest media technologies. Scholars agree that secularization theory, which assumed that modernization entails the decline of (the public significance) of religion, has lost its explanatory power. How to develop adequate theories and methods to grasp the place and role of religion in the 21st century is the burning question in the sociology of religion. In the first part, this class introduces foundational thinkers and key concepts, including the rise and critique of secularization theory and post-secular concepts. Exploring the various concrete manifestations of religion in our time (including New Age and the search for spirituality, the rise of transnational Pentecostal and Islamic movements, and the resilience of orthodox forms of Christianity), the second part presents new foci in the contemporary study of religion that help us understand how religions transform via a constant exchange with wider society.