Here are some blurbs and a direct link...
"Hitachi has developed a prototype four layer Blu-Ray disc capable of holding 100GB of data."
"Hitachi, however, claims to have used a standard Blu-Ray drive optical head that's only slightly modified to allow it to read and write data across the four 25GB layers. It's believed this will only require a firmware update to make existing drives compatible."
http://www.pcpro.co.uk/news/126871/h...uray-disc.html
Pretty freaking sweet if you ask me.