Existing taxonomies of Openness's facet structure have produced widely divergent results, and there is limited comprehensive empirical evidence about how Openness-related scales on existing personality inventories align within the 5-factor framework. In Study 1, we used a critical incidents sorting methodology to identify 11 categories of Openness measures; in Study 2, we meta-analyzed the relationships of these categories with global markers of the Big Five traits (utilizing data from 106 samples with a total sample size of N = 35,886). Our results identified 4 true facets of Openness: aestheticism, openness to sensations, nontraditionalism, and introspection. Measures of these facets were unadulterated by variance from other Big Five traits. Many traits frequently conceptualized as facets of Openness (e.g., innovation/creativity, variety-seeking, and tolerance) emerged as trait compounds that, although related to Openness, are also dependent on other Big Five traits. We discuss how Openness should be conceptualized, measured, and studied in light of the empirically based, refined taxonomy emerging from this research.