An Energy Overview - A Historical Perspective, Governmental Energy Policies, Domestic Energy Usage, Energy Imports And Exports, Fossil Fuel Production Prices

Energy is essential to life. Living creatures draw on energy flowing through the environment and convert it to forms they can use. The most fundamental energy flow for living creatures is the energy of sunlight, and the most important conversion is the act of primary production, in which plants and phytoplankton convert sunlight into biomass by photosynthesis. Earth's web of life, including human beings, rests on this foundation.

—Energy in the United States: 1635–2000, U.S. Energy Information Administration, 2001