Is there anything Serena can’t do?

World number one Serena Williams' love of fashion is well documented, but in addition to hitting great heights on the court and the catwalk, Williams is adding another string to her bow – pre-med studies.

It would seem Williams' version of taking time off is hitting the books as she takes pre-med classes, studying during tournaments in order to keep busy. Speaking as part of a panel at the Fast Company Innovation Festival, Williams said she's not sure that she wants to become a doctor but is interested in learning more about nutrition, holistic medicine, and natural healing.

"I love the holistic side of medicine," she said. Adding of her busy lifestyle: "I like to keep going. I don't like to be still."

While Williams is juggling a number of activities, her tennis career remains her number one priority.

"I think it's really important to know what you're good at – and I know what I'm good at," she explained. 

"For me right now … I love being on the court, I love winning titles. So as much as these opportunities come up, and so many things come up, but is it going to interfere with my being the best in the world? If the answer is even close to yes, then I have to say no. I have the rest of my life to figure these things out."

But that doesn't mean that Williams doesn't have time to collaborate with one of the biggest names in sport, Nike. Williams and Mark Parker, CEO of Nike, have a close working relationship and Williams contributes heavily to her attire. It's a relationship that inspires both parties.

"When I [first] stepped into Mark’s office—which was a huge inspiration in itself—it was like a wonderland of design inspiration. I was like, ‘This is really really cool!’" Williams said. "He asked, ‘What do you like? What do you wear on red carpets and the court?’ [He] was trying to find my favorite things."

"And it became such a wonderful collaboration to work with an artist who doodles in the shower," she added, referencing the fact that Parker draws new shoe designs on his shower wall.

Williams recently hit the headlines after she chased down a thief who had stolen her cellphone. When asked what she was thinking as she began the pursuit, she responded: "I wasn't, really."

"I just jumped up and I ran," she said, "and when I got there I thought, 'Oh, what am I doing, this could be it!'" But the thief, professing confusion, handed the phone back from under his sleeve. 

"The next day, she said, her father called and said, 'Serena, if you need a phone, I'll buy you three or four phones! Just please don't do that again.'"