Spring is delighted to publish this special issue on Eranos, founded in Ascona, Switzerland by Olga Frobe-Kapteyn in 1933. Spring has had a longing-standing connection to Eranos, and has published through the decades articles by many of the key figures who presented at the Eranos conferences, including works by C. G. Jung, Karl Kerenyi, Mircea Eliade, Heinrich Zimmer, Erich Neumann, Henry Corbin, Adolf Portmann, Alfred Ziegler, Gilbert Durand, James Hillman, Rudolf Ritsema, David Miller, and Wolfgang Giegerich. Eranos's pioneering endeavor of interdisciplinary conferences has been properly recognized as "one of the most creative cultural experiences in the modern Western world" and "one of the richest centers of intellectual and spiritual interchange known to our century." Its influence has been documented in a number of fields of knowledge ranging from psychology to the history of religions, from philosophy to Eastern studies, from theology to anthropology, and from biology to physics. Many of the talks given at Eranos shaped the works of some of most influential scholars of the twentieth century. Moreover, the Eranos Archive for Research in Symbolism served as the iconographic support for fundamental studies in Jungian thought and psychology. Despite the enormous amount of intellectual work, thus far only three journals have published special issues dedicated to Eranos. There has been, in fact, a singular lack of balance between Eranos's cultural importance and the attention paid to it in scholarly literature. Ultimately, even without gathering strictly historiographical works on the topic, this issue of Spring is meant to propose a reflection and a discussion on Eranos from various points of view. A first series of contributions, gathered under the title, "The Eranos Phenomenon," mainly offers an interpretation of Eranos from a historical perspective. A second series of essays, "Eranos and the Psychological Tradition," deal with Eranos's contribution to Jung's thought and then to the development of analytical psychology. The third section, "Eranos and the Idea of the Sacred," gathers a series of articles that deal with Eranos's view of the religious issues and the study of the sacred. A fourth group of articles deal with the "Philosophical Perspectives of Eranos." Lastly, a fifth series of writings, "Eranos and the Unity of Psyche and Matter," delve into Eranos's contribution to the dialogue between human sciences and natural sciences as well as between the theoretical speculation and the need for concrete answers to some crucial problems of the world we are living. This issue of Spring also includes an ample iconographic section with more than fifty photographs from the Eranos Foundation Archives, many never before published. They are products of Eranos photographers Margarita Marianne (Margarethe) Fellerer (1886- 1961), Tim N. Gidal (1909-1996), and Luciano Soave. The volume closes with a bibliographical appendix comprising a list of the Eranos Yearbooks (1933-2014) and of the Eranos Round Table Sessions (1990-2002), as well as of the proceedings of the Associazione Amici di Eranos (1990-2012) and of the Verein zur Forderung der wissenschaftlichen Tagungen von Eranos (2001-2014)."