In 1987, a PhD student at the University of Michigan named Thomas Knoll wrote a program on his Macintosh to display images, and named it Display. His brother John Knoll, an employee at Industrial Light and Magic, convinced him to turn it into an image editor. Taking a break from school, he worked on the software with his brother for six months in 1988, and renamed it ImagePro. In September 1988, Adobe decided to license the software, now called Photoshop.
And a look at how the toolstrip has evolved:
Finally, if nostalgia is your thing, here’s an interesting video showing Photoshop 1.0 in action:
Happy 20th birthday, Photoshop!