Findings from our study of undergraduate research (UR) demonstrate the multi-faceted benefits students take away from research experience in science, technology, engineering, and mathematics (STEM) fields and support many of faculty research advisors' anecdotal claims for UR. Following a dearth of empirically based research on the outcomes of UR programs, it is gratifying to have data from several recent studies that have begun to establish the nature and extent of the many benefits long claimed for UR experiences. This chapter presents findings from our comparative analysis of faculty and student perceptions of the benefits of participating in UR in the sciences and illustrates the sometimes different ways in which faculty and their students view particular areas of gain and their significance. Results from the comparative analysis show that the faculty advisors' observations largely match those of their students. As we will discuss, important distinctions emerged in the analysis in the ways in which each group perceives and values particular types of gains. Students emphasized the personal-professional transitions they experience as gains from UR. They reported shifts in their attitudes, practices, and levels of engagement as learners and apprentice researchers, and increased awareness of their temperamental aptitude for the risks and reversals inherent in authentic research. They defined these gains as having both personal and professional significance and regarded many of them as transferable to other areas of life. Faculty advisors agreed (to a greater or lesser extent) with their students' reports of the types and personal significance of their gains, but faculty also framed particular gains as evidence of their students' development as young professionals. Faculty advisors' added perspective on students' professional socialization suggests essential first steps in students' becoming scientists.