Building on the work of teacher noticing, this study investigated teachers' noticing of students' thinking evident in artifacts from their science teaching context. Prior work on teachers' noticing in science has generally focused on noticing students' thinking surrounding specific disciplinary content. We asked 20 elementary teachers to identify and discuss an artifact that represented their students' thinking in science. Rather than discuss specific disciplinary content, teachers described what students were "doing" in producing that artifact. The results of this study demonstrate attending to what students are doing is one way teachers notice students' thinking in science, and in these descriptions of "doing" lie important connections to the scientific and engineering practices of the Next Generation Science Standards. This study can inform the design of teacher learning experiences in which artifacts and teachers' tendency to focus on what students are doing can be leveraged toward learning to notice students' thinking in science.