The William and Flora Hewlett Foundation makes grants to solve social and environmental problems in the US and internationally. The foundation’s environmental sub-programme in energy and climate makes grants to strengthen global climate policy. The foundation also funds improvements in transportation to reduce air pollution, focusing on China, Mexico, Brazil and the US. Most of Hewlett’s grants are by invitation. However, the foundation accepts letters of inquiry, which can be submitted at any time, in certain programmes, including energy and climate.