We're all familiar with gigabyte and terabyte - these units measure the storage capacity of our smartphones and computer hard drives. One gigabyte comprises 1024 megabytes, while 1024 gigabytes make up one terabyte. But did you know that 1024 terabytes make up one petabyte? If you had a hard drive that could one petabyte, you could store about 13.3 years of high-definition TV video - a 50PB hard drive is said to be capable of storing every single published work known to mankind, across languages.