Fiction
Pygmalion's Spectacles is a fictional novel that probably offered the first conceptulization of virtual reality. Though it was written in the 30's, it laid the foundation for many modern VR principles. At the time, VR had not taken physical form and was only an idea.
Conception
In 1960, Morton Heilig built the Sensorama, a machine designed to stimulate the senses during the playing of a short film. He also filed for a patent for the Telesphere, which was one of the first examples of how a modern VR headset could be made and how it would look.
Science
In 1968, Ivan Sutherland created the Sword of Damolces, a ceiling mounted headset that could present wireframe rooms to the use. This device is considered the first functional head mounted display (HMD). Entities like NASA would develop their own devices, like the NASA Ames's View in 1985.
Mainstream
In the early to mid 90's, products like Virtuality and the Virtual Boy were a step towards consumer VR. Virtuality had a small library, with Dactyl Nightmare often serving as a flagship title. Its aim focused on the arcade market instead of the home market. Nintendo's Virtual Boy was released some time later and as well had its own games, including a version of Mario Tennis.
Fading
These never saw mainstream success. While the hardware was functional to a degree, it was difficult to deliver to a large audience due to cost and lesser advanced technology. The Virtual Boy in particular was criticized for being uncomfortable to use and having an unimpressive red monochrome display. Real steps toward consumer VR didn't noticeably start until research and development began in the early 2010's for headsets like the Oculus Rift.
Illusive
VR for the rest of the 90's and the 2000's was seen more as a novelty, mostly available only to research groups. It would not become a popular topic until around the mid 2010's.
Rebirth
Oculus, the company, launched a Kickstarter campaign for their first headset, the Oculus Rift, which would begin the second round of attempts to market VR as consumer and mainstream product. It helped bolster the company's development of the headset. Facebook later purchased Oculus in 2014 for roughly $2 billion.
New Age
Technology had progressed enough to not only allow Oculus to make headway with the Rift, but other companies like Valve and HTC also were working on their own VR projects around the same time as Oculus.
Plunge
The Oculus Rift CV1 (Consumer Version 1) and the HTC Vive were released in 2016. Two major VR releases since the 90's.
New Medium
The new headsets were fairly well-recieved, and managed to begin establishing VR as a new medium of entertainment. Towards the end of the 2010's, VR would increase in popularity, with several companies releaseing their own headsets. Some headsets, like the Oculus Quest and Valve Index sold well and were sometimes out of stock for periods of time.