Adobe Photoshop, the industry-standard image editor and home of the PSD document format, started life back in the late eighties when PhD student Thomas Knoll was working on his thesis - a work detailing the processing of digital images. This work evolved and in 1987 Thomas proceeded to develop an image-processing program for his Mac.

This application was created to work with greyscale images, and over a short period of time Thomas developed it further, adding new digital editing processes. It didn't take long before his brother John Knoll was intrigued by the program, dubbed Display.

John, who was working at George Lucas' Industrial Light & Magic, suggested to his brother that they turned Display into a more feature-rich fully-fledged image editing program. From here the two worked together, combining Thomas' engineering background with the design experience of his brother.

By 1988 the program had changed dramatically, with a whole host of new features and some name changes, first to ImagePro, then to Photoshop. The Knolls decided to give the project another six months, complete a beta and attempt to sell it commercially with the help of the big guns in Silicon Valley.

One company decided to give Photoshop a go, but it wasn't Adobe. A company called BarneyScan was the first to take to the brothers' software, deciding to include around 200 licensed copies of the program with its scanner hardware. It wasn't long before Adobe did become aware of the potential that Photoshop offered. In September of 1988 John Knoll gave a presentation to Adobe's internal creative team, and the rest is history.

New Kid On The Block - Adobe Photoshop 1.0

After the brothers struck a deal with Adobe their product saw an additional ten months of development time.

Finally, in February of 1990, version 1.0 of Photoshop was ready and launched exclusively for the Macintosh. It quickly defined what an image editing program should be - an impressive feat considering it only featured four named programmers on its splash screen, a stark contrast to today.

If you want to see the very first version of Photoshop in action, but with a modern twist, then check out this video of version 1.0 running on an iPhone.

Colour The Path - Adobe Photoshop 2.0

The second version of Photoshop, codenamed Fast Eddy, arrived in June of 1991 bringing with it a whole host of new features, colour splash screen included.

Version 2.0 demanded double the RAM of its predecessor, requiring 4MB to run. A brief round-up of the features added in version 2.0 include the Path tool, the Pen tool. support for CMYK, and EPS rasterisation.

Just like version 1.0, the second version was also an exclusively Mac affair. However, this all changed when 2.5 hit the market in November of 1992 - Photoshop had made its Windows debut. The other most significant feature added to 2.5 was support for 16-bit file types.

Just Like An Onion - Adobe Photoshop 3.0

Codenamed Tiger Mountain, 1994's Photoshop 3.0 for both Windows and Mac saw the introduction of one of the programs most fundamental features: layers.

Layers made the work of many a photographer and designer easier, and although Photoshop was not the first image editing program to introduce layers, it most definitely made them a commonplace feature for any graphic software package worth its salt.

Despite now being over 20 years old, some users just haven't let go. Back in 2008 a cover of the New Yorker was created with Photoshop 3.0 - and not for retro-appeal, just because the illustrator loved version 3.0 so much.

Meow - Adobe Photoshop 4.0

Two years after 3.0 arrived, its big brother - codenamed Big Electric Cat - hit shelves. Version 4.0 introduced adjustment layers and macros (known as Actions). The addition of Actions allowed for the automation of generic tasks, adding again to the time-saving appeal of the Photoshop product.

Photoshop 4.0 also saw several interface changes, bringing it more in line with other Adobe products.

Lasso That Cargo - Adobe Photoshop 5.0

During May, 1998, Adobe shipped Photoshop 5.0, known as Strange Cargo while in development. With it came such important features as the Magnetic Lasso, editable type, and the History panel.

The History panel allowed the user to undo an action multiple times to reach an earlier state - handy stuff!

1999's version 5.5 release saw the addition of Save For Web, a feature added specifically to format images for the Web, resulting in better compression

Shiny shiny: Adobe Photoshop 6.0

Codenamed Venus In Furs, the first major release of the new millenium was version 6.0, which hit the shelves in September 2000.

Changes and new features introduced in this version include various changes to the user interface, the Liquify filter, Vector Shape support, and improvements to layer styles interface, to name a few.

Adding to the web-friendly features introduced in 5.5, version 6.0 added layer-based slicing - handy for web-layout work.

Paint The Sky - Adobe Photoshop 7.0

Version 7.0 of Photoshop, codenamed Liquid Sky, arrived in 2002.

It was the last major version with a numerical-only suffix, and also the last to run on the classic Mac OS 9. In 2003 Adobe released the Camera RAW plugin for Photoshop 7.0, adding the ability to manipulate digital data from an ever-growing range of cameras.