Professor Stephen Guggenheim arrived in the summer of 1976 in the Department of Geological Sciences, as the Department was called then, after receiving his Ph.D. from the University of Wisconsin in Madison, Wisconsin. Over the years, Steve explored his research interests in mineral chemistry, specializing in clays and environmental mineralogy. He has over 110 publications, including high profile scientific journal articles and 13 book chapters, culminating in over 2700 citations. In addition, he has co-edited several books and journal volumes, including Baseline Studies of the Clay Minerals Society Source Clays, Micas: Crystal Chemistry and Metamorphic Petrology, and Teaching Clay Science. In recognition of the quality of his early research, he received the Hawley Medal of the Mineralogical Association of Canada for the best paper of 1986. Later he received the AIPEA Medal for Research Excellence for 2005-09, presented by the Association Internationale pour L’Etudes des Argiles (International Association for the Study of Clays). In 2013, he received the Marilyn and Sturges W. Bailey Distinguished Member Award of the Clay Minerals Society (of North America). As a crowning achievement, Steve was elected in 2007 as Foreign Member of the Accademia Nazionale dei Lincei (Italian Academy of Sciences and Humanities). Steve dedicated his time to teaching both introductory and upper level courses including Mineralogy and Crystal Chemistry. In 1997, the quality of his teaching was recognized by the University of Illinois at Chicago, when he received the UIC Teaching Recognition Award. In his service to the academic community, Steve has held many leadership roles. In 1996-1997, he was president of the Clay Minerals Society (1996-1997), and from 1998-2001, he was Editor-in-Chief of Clays and Clay Minerals. Steve clearly has been very active in his professional career, and he promises to continue his scientific endeavors for many years to come. We like to thank him and wish him well.