The high-definition movie disc battle between HD DVD and Blu-ray Disc can be traced all the way back to 2000, when companies began experimenting with using new blue lasers in optical disc systems.

Because the wavelength of blue light is shorter than that of the red lasers used in DVD, less physical space is needed to record each bit of data and so more information can be crammed onto a DVD-sized disc. This extra space was needed to store the new high-definition video and TV services that were starting to be commercialized around that time.

But what started in 2000 as technical research became a battle between the world's largest electronics companies and movie studios, with the consumer caught in the middle.

Here's a look at the major milestones from the first research:

2000

October 5 -- Sony and Pioneer unveil DVR Blue at Japan's Ceatec show. The format would go on to form the basis for first-generation Blu-ray Disc BD-RE.

November 1 -- Sony announces the development of Ultra Density Optical (UDO), a blue-laser optical disc format proposed to replace magneto-optical discs.

2002

February 19 -- Led by Sony, nine of the world's largest electronics companies unveil plans for Blu-ray Disc.

August 29 -- Toshiba and NEC propose to the DVD Forum the next-generation optical disc format that will become HD DVD.

October 1 -- Prototypes of both formats are unveiled at Japan's Ceatec exhibition. Sony, Panasonic, Sharp, Pioneer and JVC showed prototype Blu-ray Disc recorders while Toshiba showed a prototype under the name Advanced Optical Disc (AOD).

2003

February 13 -- Licensing of Blu-ray Disc begins. Player makers pay US$20,000 to license Blu-ray while the content-protection system license carries a US$120,000 annual fee and additional charge of US$0.10 per player. Media makers pay US$8,000 annually and US$0.02 per disc for the copy protection system.

April 7 -- Sony announces its Blu-ray Disc-based Professional Disc format for data archiving applications.

April 10 -- Sony puts on sale in Japan the world's first Blu-ray Disc recorder, the BDZ-S77. It's based on a 23G-byte cartridge version of the BD-RE disc and costs YEN 450,000 (US$3,815 at the time). The machine and a later model from Panasonic lack support for prerecorded movies that will launch later and prove an expensive early step into next-generation video.

May 28 -- Mitsubishi Electric joins the Blu-ray Disc group.