Program Participation. Of the transfer students that signed up for the TSMP, all 35 juniors were matched with a graduate student mentor for the semester. Based on graduate student mentor survey responses, approximately 85% of mentees met with their mentors at least once over the course of the fall semester. Among both graduate and transfer student respondents, the median number of individual meetings per student-mentor pair over the course of the semester was three with a median absolute difference of 1 (Figure ). Of the mentors in our program responding to the survey, nine of the thirteen graduate student mentors had previous one-on-one mentorship experience, which included instances such as mentorship of an undergraduate and/or a more junior graduate student in their research lab, tutoring, and participation in a formalized mentorship program such as the ChemMentor Program at UC Berkeley, which pairs incoming graduate students with current graduate students in small mentorship groups. All mentors were expected to have had experience as a teaching assistant based on UC Berkeley's graduate student teaching requirement. Of the six total seminars hosted, both transfer student and graduate student mentor respondents reported attending a median of three seminars with a median absolute difference of zero for graduate student mentors and 1.5 for transfer students. International Public License. Ten questions asking for a Likert scale-type response to cartoons paired with statements reflecting sense of belonging in a graduate program were used to assess sense of belonging of both transfer and graduate students. While the statements used had previously been validated as measuring sense of belonging in a graduate student population, they had not previously been used to measure sense of belonging in undergraduates. To probe the internal consistency of our scale when measuring sense of belonging of undergraduates, we calculated Cronbach's a for both the beginning and ending Likert-type survey responses after inverting responses to statements corresponding with a negative sense of belonging so that a high score always indicated higher sense of belonging. The responses were found to be consistent with the exception of the phrase "I'm grateful to have a supportive social network" for both transfer and graduate student respondents, with Cronbach's a values of 0.72 or higher for all populations (Table -S4). We additionally included qualitative questions to allow respondents to further clarify feelings of sense of belonging and science identity in their own words. These questions along with a selection of responses are outlined in Table and. All statistical analyses were performed in Microsoft Excel for Mac, Version 16.59. Ten (10) TSMP undergraduates and 13 graduate student mentors completed the August survey, 12 TSMP undergraduates and 13 graduate student mentors completed the December survey, and 16 graduate student mentors completed the follow-up survey in March. This corresponds to 29% of the TSMP participants and 65-80% of the graduate student mentors. In addition, we recruited eight and seven students from the general transfer student population to participate in the initial and final surveys, respectively, as a comparison group (non-TSMP).