millions of americans are now use go-pro cameras giving those of us in the news business amazing pictures. >> for go-pro founder it's money in the bank. his net worth is now nearly $4 billion. here's david muir who met with him to take it all in. >> reporter: the corner of fifth avenue and west 33rd street in new york. >> hi, guys. >> reporter: while they are waiting for us with their own cameras. the inventor of the go-pro. right there with a camera for me and a camera for him. we begin our walk through the empire state building. we meet cesar, part of the security team. you can see the small go-pro he's carrying an what they call an extender. a man-made arm. this is the first time he's tested out his cameras at the empire state building. nick woodman came up with the idea. just 26. he's a surfer.