In this chapter, we will focus on when it is time to grow, including developing your role as a mentor, growing your research team, and developing collaborations across research groups. The early activities of developing and organizing your research team were covered in chapter “ Your Team: Mentors, Staff, Colleagues, and Mentees.” That included seeking mentors, developing a research team, cultivating relationships with colleagues, and leveraging your early experiences as a mentor to others. All of these groups (your mentors, your team, your colleagues) form the innermost circle of your SEM. Chapter “ Expanding Your Team” therefore represents the next step-up. These activities are typically more common at the mid-career level, after you have achieved the early hurdles of career development programs and grants and have a good grasp of your area of research and skill set. Unfortunately, this is often a time when you have less available resources for guidance and information about these important milestones of expansion. So, stay strong! You still can rock your science when it is not just YOU!