This paper explores how generative AI (GenAI) dramatically expands the scope and capabilities of automation in work, education, and everyday life, posing both risks and opportunities for cognitive capabilities. The CHI 2025 workshop sought to bridge the science of how GenAI uses to impact human thinking (e.g., metacognition, critical thinking, memory, and creativity) with research on the design and implementation of GenAI tools. Fifty-six researchers, designers, and thinkers gathered for a day of discussion, ideation, and community building, drawing on 34 papers and portfolios. This paper synthesizes these findings to map the landscape of research and design opportunities and foster a multidisciplinary community around this important research area.