Middle school Black girls in the Chicagoland area encounter challenges when engaging in Science Technology Engineering and Math (STEM) learning and developing individual STEM identities. Black girls with good grades in STEM courses are reluctant to pursue STEM careers because of the negative stereotypes they face in school (King & Pringle, 2019), (Lane & Id-Deen,2020). My problem of practice focused on the challenges these girls may encounter when developing individual STEM identities. My dissertation in practice research aimed to reduce the barriers that Black middle school girls encounter when developing individual STEM identities. This inquiry pilot program, known as the Girls Invent Mentorship, engaged middle school girls in partnership with University of Chicago female science mentors (graduate and undergraduate students). Girls (mentees) and female science mentors used an inquiry-based, hands-on science curriculum developed by the Illinois Student Invention Convention (ISIC) organization. This mixed method research (Mertens, 2010) project collected data in the form of photos, written science content produced by the girls, science mentors' reflections, and documented observations taken by me in my role as the program manager. The research data and observations focused on three girls and their STEM identity development while mentors reflected on their STEM career paths. Each case study highlights the journey of a girl as they develop STEM identities throughout this research study. Data collected revealed trends which included girls having STEM identities along a continuum, strong STEAM identities, and increasing science skills across learning spaces (formal and informal). Girls who engaged with female scientists at the university for several Saturdays showed increased interest in STEM careers and STEM learning. This pilot program provided insight into the development of a framework that could be used for future STEM mentorship programs hosting middle school girls. In conclusion, this study explored ways in which a mentorship program could support the development of positive STEM identities and foster an increased interest in STEM careers in Chicago area middle school Black girls. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]