It is a good practice to try to understand matters at hand by first stepping back and adopting an historical perspective, which I will begin this review by doing. Next, I will take up the challenges that each of the authors in the articles in this volume has presented for the study of complexity, accuracy, and fluency (CAF) in second language acquisition. Finally, I will conclude by issuing a few challenges of my own, along with proposing a broader frame in which to situate the study of CAF.