In the two decades since the debut of the Digital Earth (DE) vision, a con-certed international effort has engaged in nurturing the development of a technologyframework and harnessing applications to preserve the planet and sustain humansocieties. Evolutionary threads can be traced to key historic and multidisciplinaryfoundations, which were presciently articulated and represented at the first Inter-national Symposium on Digital Earth hosted by the Chinese Academy of Sciencesin 1999. Pioneering groups in government, industry, and academia have cultivatedthis fertile futuristic conceptual model with technological incubation and exploratoryapplications. An array of space-age developments in computers, the internet and com-munications, Earth observation satellites, and spatially oriented applications sparkedan innovative discipline. TheBeijing Declaration on Digital Earthis recognized forits role in promulgating the series of International Symposia on Digital Earth topromote understanding of the impacts of DE technology and applications on behalfof humankind. Combinations of industrial, academic, and government organizationshave rapidly advanced the technological components necessary for implementing theDE vision. Commercial leaders such as Google have accelerated the influence of DEfor large segments of society. Challenges remain regarding requisite collaborationon international standards to optimize and accelerate DE implementation scenarios.This chapter provides an overview of the DE initiative and basic framework, theglobal response to DE, the evolution of DE, its relationship to key global scienceinitiatives, and the response to global challenges.