This volume is both a state-of-the-art display of current thinking on second language development as a complex system. It is also a tribute to Diane Larsen-Freeman for her decades of intellectual leadership in the academic disciplines of applied linguistics and second language acquisition. The chapters therein range from theoretical expositions to methodological analyses, pedagogical proposals, and conceptual frameworks for future research. In a balanced and in-depth manner, the authors provide a comprehensive and interdisciplinary understanding of second language development, with a wealth of insights that promise to break the status-quo of current research and take it to exciting new territory.