Complex sentence: In what is perhaps his most well-known contribution, he and his colleagues (Celso Grebogi and James A. Yorke) have shown that dynamics on a chaotic attractor can be controlled by using only small perturbations.
Split into simpler sentences: In what is perhaps his most well-known contribution, he and his colleagues (Celso Grebogi and James A. Yorke) introduced the idea of controlling chaos. In particular, they have shown that dynamics on a chaotic attractor can be controlled by using only small perturbations.