Constructivism sees learning as the construction of knowledge based on experiences. Students learn by actively engaging in their environment and building on prior knowledge. Two key theorists are Piaget, who believed children learn through organizing their experiences, and Vygotsky, who emphasized social interaction and the "zone of proximal development," which is the gap between independent and assisted problem solving. A constructivist classroom is student-centered, uses cooperative learning, and links activities to real-world contexts.