Glass Crystallization Research — A 36-Year Retrospective. Part I, Fundamental Studies † Edgar D. Zanotto* ,‡ Department of Materials Engineering, Vitreous Materials Laboratory – LaMaV, Federal University of São Carlos, 13.565-905, São Carlos, SP Brazil Over the past 36 years, our research has mainly focused on the crystallization kinetics and properties of glasses and glass-ceramics. A sampling of the most conclusive papers are reviewed here and include the following topics: the effects of liquid phase separation on crystal nucleation; tests and development of models of crystal nucleation, growth, and overall crystallization; metastable phase formation; surface crystallization; glass stability against devitrification; glass-forming ability; possible correlations between the molecular structure and the nucleation mechanism; sintering with concurrent surface crystal- lization; and diffusional processes that control crystallization. We conclude that despite significant advancement in the knowl- edge about several aspects of phase transformations in glasses that resulted from our own research and of other groups, which is not described in this review, glass crystallization remains an open, rich field to be explored. Introduction I begin with apologies because this article is based on my 2012 G. W. Morey award talk; therefore, I only summarized and discuss work on glass crystallization processes from our own group and collaborators and, as a result, leave aside several important papers published by other authors. In addition, due to space restrictions, no equations, figures or other details are shown in this review paper; the interested reader is cordially invited to consult the cited references for further details. The nature and kinetics of crystallization is a vital scientific problem that governs the glass-forming ability (GFA) of molten liquids and the ultimate stability (GS) of glass against devitrification. Over the last 36 years, our research has mainly focused on funda- mental studies of glass crystallization. The first step of the crystallization process — nucleation — is essentially a nanoscale phenomenon that faces some difficulties, not only on the theoretical side, but also in the choice and application of experimental techniques and inter- pretation of results. However, such studies are essential for understanding the vitreous state, as we will show in this article, and for the successful development of useful glass-ceramics, which are described in Part II. 1 Our strategy has been to strike a balance between purely fun- damental research and some technological development; *Member, The American Ceramic Society. † Article based on the G. W. Morey award talk delivered at the Glass and Optical Materials Division meeting, ACerS, Saint Louis, MO, USA, May 2012. ‡ dedz@ufscar.br © 2013 The American Ceramic Society and Wiley Periodicals, Inc International Journal of Applied Glass Science 4 [2] 105–116 (2013) DOI:10.1111/ijag.12022