We believe that science journals can be used in the preschool classroom as tools for supporting and assessing children's learning of science- and literacy-relevant content and procedures. To support this argument, we review changes in attitudes about the cognitive competencies of preschoolers and in teaching and learning expectations for early childhood education. We describe practical aspects of using science notebooks with this age group and discuss specific ways that journals support children's learning. Finally, the role of journals in assessment is discussed.