Houston is recognized worldwide for its energy industry—particularly for oil and natural gas—as well as for biomedical research and aeronautics. Renewable energy sources—wind and solar—are also growing economic bases in the city. The Houston Ship Channel is also a large part of Houston's economic base. Because of these strengths, Houston is designated as a global city by the Globalization and World Cities Study Group and Network and global management consulting firm A.T. Kearney. The Houston area is the top U.S. market for exports, surpassing New York City in 2013, according to data released by the U.S. Department of Commerce's International Trade Administration. In 2012, the Houston–The Woodlands–Sugar Land area recorded $110.3 billion in merchandise exports. Petroleum products, chemicals, and oil and gas extraction equipment accounted for approximately two-thirds of the metropolitan area's exports last year. The Top 3 destinations for exports were Mexico, Canada, and Brazil.
Besides oil and gas, what is Houston known for? (If the question is unanswerable, say "unanswerable")
biomedical research and aeronautics