Summary:

- The article discusses the field of sustainability science, which aims to understand the interactions between human and environmental systems and develop solutions to complex sustainability challenges.

- It highlights three key questions that sustainability scientists are grappling with: how to address the growing global population and resource demands, how to create more sustainable and resilient urban systems, and how to foster the necessary societal transformations to achieve sustainability.

- The article emphasizes the interdisciplinary nature of sustainability science, which requires collaboration across fields such as engineering, social sciences, and policy, and the need for a long-term, systems-level approach to tackle these complex, interconnected challenges.