More recently than nuclear, wind, or solar, the development of the shale gas industry and subsequent boom in shale gas development in the United States was enabled through government support.[31][32] The history of shale gas fracking in the United States was punctuated by the successive developments of massive hydraulic fracturing (MHF), microseismic imaging, horizontal drilling, and other key innovations that when combined made the once unreachable energy resource technically recoverable. Along each stage of the innovation pipeline – from basic research to applied R&D to cost-sharing on demonstration projects to tax policy support for deployment – public-private partnerships and federal investments helped push hydraulic fracturing in shale into full commercial competitiveness. Through a combination of federally funded geologic research beginning in the 1970s, public-private collaboration on demonstration project and R&D priorities, and tax policy support for unconventional technologies, the federal government played a key role in the development of shale gas in the United States.