Facebook CEO Mark Zuckerberg made his first trip to Texas this week — and became one of the most famous people to take the stand in Dallas’ federal courthouse. In his testimony, the 32-year-old co-founder of the giant social media company offered a glimpse into the fast-paced, ambitious culture of Silicon Valley and the promise he sees in virtual reality, an immersive computer-generated experience that uses audio and video to simulate real-life scenes.