Teacher identity development and change is shaped by the interrelationship between personal biography and experience and professional knowledge linked to the teaching environment, students, subject matter, and culture of the school. Working from this framework, this study examines how beginning teacher interns who are part of an alternative route to teacher certification construct a professional identity as science educators in response to the needs and interests of urban youth. From the teacher interns, we learn that crafting a professional identity as a middle-level science teacher involves creating a culture around science instruction driven by imagining "what can be," essentially a vision for a quality and inclusive science curriculum implicating science content, teaching methods, and relationships with their students. The study has important implications for the preparation of a stronger and more diverse teaching force able to provide effective and inclusive science education for all youth. It also suggests the need for greater attention to personal and professional experience and perceptions as critical to the development of a meaningful teacher practice in science.