While there is little doubt that substantial progress has been made in identifying teacher behaviors and other variables that can promote meaningful learning consistent with contemporary standards, these comments are also valid at this writing 20 years later. That said, the assumption that laboratory experiences help students understand materials, phenomena, concepts, models, and relationships, almost independent of the nature of the laboratory experience, continues to be widespread in spite of sparse data from carefully designed and conducted studies. A more recent assertion is that laboratory experiences can help students develop ideas about the nature of a scientific community and the nature of science. During the past 20 years substantial new knowledge has been developed about cognitive development, the learning of science, and the nature of science. This new knowledge has fueled many ideas about ways the introductory sciences should be taught to promote understanding. In addition, significant changes in computer technologies offer substantive new tools and resources for empowering teaching and learning science that can complement experiences in the school laboratory. Moreover, more sensitive social science research methodologies have been developed that enable science education researchers to examine more carefully the ideas of students and their teachers and the effects of a variety of learning environment variables on the development of students’ concepts, skills, motivation, and attitudes.