The CAM flora is currently at a crossroads, where the high diversity of CAM species is under severe threat from human-caused global change, yet their utility for humanity is on the verge of rapid expansion. Our understanding of CAM is relatively recent, being just over 50 years old. Through-out most of the time humanity has known of CAM, Professor Klaus Winter has been a leading researcher of CAM biology. On the fiftieth anniversary of Klaus’s first CAM publication, the Editors of the Annals of Botany have commissioned a special issue to honor his accomplishments in CAM research. Through a series of review papers, perspectives and original research reports, the Special Issue will consider CAM origins and the future of CAM. “CAM Origins” will include reviews addressing the evolutionary diversification of CAM and the environmental imperatives favoring CAM evolution. “CAM Futures” will look at the impacts of global change on the CAM flora, and how humanity is developing new CAM varieties to address major challenges in food production, resource use on marginal lands, bioenergy, and climate change mitigation.