This article seeks answers to questions, such as how children's writing develops and how young students express themselves in writing at various stages of their development. This article reviews the literature through a wide lens as it examines elementary students' writing and is intended to lead to a more comprehensive understanding of developmental, cognitive, social cognitive, and sociocultural variables that impact writing. Research indicates that as children gain more expertise in writing, they tend to focus more on content and their audience rather than the surface structures of their text. They become more able and willing to make substantial and meaningful revisions in their text and consider that process as a part of writing rather than an add-on activity focusing on superficialities. Error avoidance and knowledge-telling' are replaced by knowledge transformation and meaningful communication that result in qualitatively different writing. Of course, teachers play a major role in this development as what they tend to focus on in class becomes the focus for their children as they learn to express themselves. Even though younger elementary students have fewer automated skills and their cognitive resources are spent on mostly local tasks, they can function as competent problem solvers and writers. They just need scaffolding and instruction based on the understanding that children's cognitive processes are also impacted by their literacy environment and community. Once these general theories of cognition, development, and socialization are well understood, research-based curricula and effective instruction based on best practices can be designed to improve children's writing achievement.