Michael Buckwald and David Holz, a pair of unassuming twentysomethings from Florida, arrived in San Francisco in 2010 with two 30-pound backpacks slung over their shoulders.

In the bags was the earliest prototype of what would become the Leap Motion controller, a computer accessory that uses tiny embedded cameras and LEDs to track a user's hand movements. The device, which is expected to ship to customers this summer, is a bit like the Xbox Kinect, only about 200 times more accurate: Leap's sensors track finger movement within 10 microns. (The width of an average strand of human hair is about 100 microns.)

The Leap Motion controller may very well be a game changer in computing. The company, which began taking pre-orders for the $80 device last year, has already tallied hundreds of thousands of orders. To keep up with the manufacturing demand, Buckwald and Holz raised $30 million from venture capitalists, bringing the company's total funding to about $45 million.

Here's how Buckwald and Holz took the Leap Motion controller from a complex math equation to the shelves of Best Buy.

2010: "It was time to start a company." 

Buckwald and Holz have been friends since middle school. They stayed in touch throughout college, but Buckwald, who had an interest in entrepreneurship, never imagined he and Holz would eventually go into business together.

Buckwald: In college, I started a company called Zazuba, which I sold to Yellow Pages. I was looking for the next thing that I wanted to work on. David was getting his math Ph.D. and came to visit me.

Holz: I was doing applied mathematics in graduate school, working for NASA on the side, and building what would become the first versions of Leap. My thinking was, instead of solving one problem, I'd rather make it easier for people to solve multiple problems.

Buckwald: Even though a 5-year-old can build a clay cup in minutes, it would take a professional modeler hours to do the same thing on a computer. That's not because computers aren't powerful; it's that there are barriers between humans and the computer. David's technology would break down those barriers. We decided it was time to start a company.

2011: The crude prototype

After cobbling together a prototype out of parts from Radio Shack, the friends moved to San Francisco and began pitching their idea to venture capital firms.

Buckwald: Our goal was to raise money and hire some great people to help us create a useful product. Our first prototype had to be carried around in two backpacks. It weighed a lot and took a long time to set up. It was basically a Logitech webcam and a bunch of LEDs in plastic Radio Shack cases, duct-taped together and connected to a laptop.

It could track only one finger. Still, we were talking to investors and selling a vision that we wanted to fundamentally change how humans interact with computers. People were skeptical.

The turning point of investor meetings was when they got past the look of the device and put their fingers in front of it to control something. We'd let them play games, like Fruit Ninja. It was crude, but our prototype was still orders of magnitude faster and more accurate than existing gesturing devices. It was a very powerful experience to feel connected to a computer like that. Even the skeptics were blown away by how fast it was.

2012: A dozen versions later...

Buckwald and Holz raised about $15 million and hired about 50 employees to help them refine their design. When the company began taking preorders in early 2012, demand was so high that Buckwald and Holz hit up investors for another $30 million to step up production.

Holz: We went through major revisions of the components many times in order to make the Leap smaller and smaller.

Buckwald: Getting the size down was important, because we wanted to be able to embed this technology in other devices. We probably talked to more than 30 lens manufacturers to find lenses small enough that had a wide-field view. People said it was impossible. But we didn't take no for an answer.

We had to convince suppliers that this product would be disruptive and would create new opportunities for them. Our devices would have been twice as tall if we had used lenses that existed off the shelf at the time that we started making Leap.

Holz: We also wanted it to feel sturdy. Originally, we were going to go with plastic, but we went with aluminum. It wasn't 10 times more expensive, but there's a cost for quality.

2013: Ramping up for launch

The co-founders announced deals with Best Buy (to carry the Leap Motion controller in its stores) and HP (to embed Leap's technology into its products). Leap produced more than 600,000 devices, but owing to software issues, the founders pushed back the launch date from May to July.

Buckwald: We have only one opportunity to launch. Just one opportunity to prove to the world that this type of control--with the accuracy Leap Motion has-;is a better way of interacting with computers. To do that, we have to take a little bit of a delay and spend a little extra time and energy on polish.

One of the greatest opportunities for this technology is to let regular people do things they just can't do today with computers. Our approach has never been used before in academia or in industry-;it's built on top of advances in pure math. The biggest advantage we have is that the company was not created to make products that make money. It was built by David to solve this very specific problem.

We're in the office 12 to 15 hours a day, six or seven days a week, but it doesn't feel like work. It's been a lot of fun, and it continues to be a lot of fun.