The topic of teacher noticing has been refined in the mathematics education literature over the last 15 years. Researchers who study noticing have established a complex definition of this process, which encompasses how a teacher identifies, evaluates, and considers responding to a student's classroom contribution. They have also developed a variety of techniques to measure a teacher's capacity to engage in noticing and have documented how this capacity can change over time with certain interventions or experiences. Science education researchers have more recently begun studying noticing. Among other results, their efforts have yielded the concept of responsiveness to further the examination of a teacher's classroom actions in response to student contributions. This brief review article traces research in noticing from its origin in mathematics education to its current manifestation as responsiveness in science education. A synthesis of the research and suggestions for future studies are provided.