This lecture by the instructor covers the challenges and innovations in the sanitation economy, focusing on the nexus between water, sanitation, and hygiene. It discusses the global lack of access to sanitation, the impact of unsafe water, and the economic costs of inadequate sanitation. The lecture explores the potential of new sanitation systems, markets, and economies, emphasizing the importance of renewable resources and data-driven approaches. It also delves into smart sanitation business models, digital public health monitoring, and nature-based solutions for resilient sanitation systems. The presentation concludes by encouraging the audience to imagine innovations in various sanitation-related categories.