NASA is developing a two-phased approach to quickly return humans to the Moon and establish a sustainable presence in orbit and on the surface. The two phases run in parallel, and both have already begun, with selection of the first Gateway element, the Power and Propulsion Element, solicitation activities focused on an American-built, industry-provided Human Landing System, and discussions with industry and international partners about potential opportunities for collaboration. Phase 1 is driven exclusively by the administration's priority to land the first woman and the next man on the lunar South Pole by 2024. In this phase, NASA and its partners will develop and deploy two Gateway components: the Power and Propulsion Element (PPE) that will launch in 2022, and the Habitation and Logistics Outpost (HALO), a minimal habitation capability) that will launch in 2023. Both will launch on commercial rockets, as will Gateway logistics deliveries to outfit the ship and provide supplies for surface expeditions. This initial Gateway configuration represents the beginning of its capability buildup, and the primary components required to support the first human expedition to the lunar South Pole. NASA's baseline reference approach for human expeditions on the surface is for Human Landing Systems to aggregate and dock to the Gateway, then deploy to the lunar South Pole with two astronauts aboard. Phase 2 is focused on advancing the technologies that will foster a sustainable presence on and around the Moon - a lasting and productive presence enabled by reusable systems, access for a diverse body of contributing partners, and repeatable trips to multiple destinations across the lunar surface. In this Phase, we will advance sustainable systems to make surface expeditions more repeatable and affordable. While the Gateway is the first of its kind to be funded, the concept has been proposed for decades as a necessary and foundational capability for a sustainable return to the Moon, and a port for vehicles embarking to farther destinations. It supports every tenet of Space Policy Directive-1 and the infrastructure it provides is critical to an accelerated return to the Moon, and access to more parts of the Moon than ever before. The Gateway also provides a unique platform to conduct cross-discipline science. Science instruments, both internal and external to the Gateway, have the potential to reveal new findings in space science, Earth science, and biological research data from deep space. Additionally, the broad science community will be able to utilize the communications and data relay capabilities of the Gateway, beginning with the PPE in Phase 1. This paper will outline the cross-discipline activities NASA is currently conducting, and those the agency anticipates conducting in the future to successfully implement Phases 1 and 2 in the lunar vicinity, all while preparing for humanity's next giant leap: Mars.