The Chapter 4.17 has described the geological evolution of the Great Lakes and their hydrology and introduced selected features of lake physics, chemistry, and biology. In this chapter, two of the most important pollutant classes in the Great Lakes, nutrients and persistent bioaccumulative toxins, and biogeochemically mediated interactions between water, atmosphere, and lake sediments are examined. Next, the role of satellite remote sensing in enhancing our understanding these features of lake behavior is reviewed. Finally, policy and the regulatory environment, the bases for management of sustainable futures is looked at. As with the previous chapter, two key points are emphasized: (1) we should look to nature before the fact for help in differentiating sustainable and unsustainable practices and (2) it is critical that we increase our awareness of those things that ‘we don't know we don't know’ about the response of the Great Lakes to human perturbation. Adoption of an outlook that embraces an ethic, sensitivity, and understanding represents an excellent start to ensuring a sustainable future for these Great Lakes.