The Howard Hughes Medical Institute is one of the largest private medical research funding institutes and the second largest philanthropic organization in the United States.
It was founded by billionaire Howard Hughes in 1953 in order to comply with a demand by the United States Defence Department that Hughes divest himself of his ownership interest in Hughes Aircraft, a major defense contractor. However, until Hughes' death, it was under consistent review by the IRS which challenged its status as a non-profit.
However, with Hughes' death in 1976, the stock in Hughes Aircraft passed to its trustees despite disputes over Hughes' will. The trustees eventually sold the stock to General Motors for the equivalent of $5.4 billion in cash and stock. It currently has an endowment of $19 billion and spends over $800 million dollars a year funding research.Howard Hughes Medical Institute at Wikipedia