The interdisciplinary study of Michelangelo's creative process deviates from art-historical studies of the creative product and those of the artistic process, defined in terms of stylistic or iconographic development, chronology or dating. It examines the dynamic process that constitutes the essence of creative activity by combining the tools and methods of art-historical research with the definitions and approach of cognitive psychological theory and research in creativity in order to identify and interpret cognitive processes exhibited in the formative stages of the Sistine ceiling and the Medici Chapel. Conclusions are based on an objective, methodological study of visual evidence in an art-historical context. Cognitive patterns, preferences for certain formal structures, ways of dealing with conflict and constraint in the artistic process, and other psychological strategies are reconstructed primarily from the artist preparatory sketches. While certain patterns were found to be consistent in Michelangelo's creative process during the period studied, sig­nificant changes reflect the artist's development.