Geologic CO 2 sequestration is a promising option to mitigate adverse effects of climate change. To ensure its environmental sustainability, we must understand key geochemical reactions (from nano-scale to reservoir-scale) and their impacts on the reactive transport of CO 2 and on environmental risk management. See Jun and co-workers, es304681x. The cover art images were contributed by: Brook Haley, Daniel Byers, Rob Finley, Quanlin Zhou, Jens Birkholzer, Jiamin Wan, Yongman Kim, and Yandi Hu. We are grateful to Dean Ralph Quatrano (WUStL) for his support. View the article.