This practice guide helps changemakers explore and find new pathways to accelerate sustainable development in an uncertain world. It captures and celebrates six years of developing and testing R&D practice across 115 countries through the UNDP Accelerator Labs network. This guide describes ways of engaging with complexity through collective learning and action: building on local knowledge, amplifying grassroots innovation, exploring possible futures with communities, and experimenting with new technology and non-traditional data sources. It offers practices that help us become smarter together and enable our innovation and development initiatives to take transformative leaps forward.