These manifest themselves as rumors. Soon rumor gets the attention of the press through press reports. Products come out. Periodicals spring up and begin promoting the new wave of the future. Before long players emerge to ride the wave.
Waves vary in size from the small market to the huge tsunami of the Internet.
Each wave crests and breaks. The break sets off new ripples. Some dissipate, while others begin to swell into their own waves. This is the nature of technology. Look to the sea and watch the ripples.