If you follow Mac history you will enjoy a blast from the past in 20 Years of Adobe Photoshop from WebDesignerDepot. Photoshop started as the creation of brothers Thomas and Glen Knoll:
Thomas Knoll was a PHD student studying Engineering at the University of Michigan. His brother was working at Industrial Light and Magic. Thomas Knoll wrote a subroutine for a program to translate monochrome images on his monitor to grayscale. The successful subroutine led Knoll to create more and very soon he had a number of processes for achieving photographic effects on digital images. After his brother John saw what Thomas was doing, he recommended that Thomas turn what he was doing into a full-featured image editor.
That image editor became a full-fledged product in 1988. ImagePro.
They called on Supermac and Aldus, but were turned away at both, a move that Aldus would come to seriously regret. Shortly after, the Knoll brothers struck gold when they won over Adobe management with their product, and formed a licensing partnership with Adobe that was to launch their software and Adobe into the stratosphere. In February of 1990, Adobe Photoshop 1.0 was released.
The rest is history.