Book excerpt: Currently, the reliance on fossil fuels raises concerns on the increasing global energy demand, the rapid anthropogenic climate changes and growing environmental problems. The grand challenge is to search for viable carbon-neutral sources of renewable energy. Nanomaterials are arguably the base that integrates nanotechnology, information technology, and biotechnology; the major drivers of technological development today. Over the past decades, the understanding of form-function relations surrounding nanomaterials has significantly brightened the prospects of the transition from fossil fuels to solar fuels. This book introduces the latest developments in nanomaterials aimed at the applications in clean energy areas. It overviews the close link between nanomaterials development and energy applications from the experience and perspective of the authors. It discusses the bottom-up synthesis and interface engineering of new materials of different dimensions and describes their applications in future energy devices such as secondary batteries, novel solar cells, luminescent devices, and water splitting electrolyzers. .