We know little about diverse youths’ engagement in science outside of school, the form such engagement takes and its impact on science literacy development and identity as a potential insider to science. We need to know more about why, how, and for whom out-of-school settings make a difference. Science in the Making at the Margin offers some answers through an in-depth and theoretically well-grounded multisited ethnography of three very different out-of-school settings: an afterschool program for girls only, a youth garden program, and a Math and Science Upward Bound Program. Grounded in sociocultural-historical theory, this book explores, youths’ meaning making of science and co-constructions of new levels of understandings of science, as well as how they come to position themselves in relation to science through participation in science practices at the margin. The author highlights the multiplicity of learning, becoming and hybridity that constitute the learning of science in the three sites studied. Her analysis suggests that most youth position themselves as science users, as youth who are creating with and learning through science with others in textually rich environments and situations, and in ways that are meaningful to them. Their identity as users of science is grounded in the forms of engagement supported by the three science practices. The challenge is then to leverage such literacy beyond the practices themselves.