Houston is the most populous city in the state of Texas and is currently the fourth most populous city in the United States. Exponent has operated an office in the greater Houston area for 30 years. Houston is home to the NASA Johnson Space Center, the Texas Medical Center and to the renowned Houston Grand Opera. Listed second in the number of Fortune 500 companies headquartered within its city limits, the Houston economy has a broad industrial base in energy, manufacturing, aeronautics, construction, and transportation. With strengths in business, international trade, entertainment, culture, media, fashion, science, sports, technology, education, medicine, and research, Houston continues to be a sprawling metropolis with a growing diverse population.