Researchers at the University of Southampton in the UK successfully stored the entirety of the human genome sequence onto an indestructible 5D optical memory crystal no bigger than a penny. The indestructibility claims are no joke since the discs can withstand temperatures up to 1,000°C, cosmic radiation, and even direct impact forces of 10 tons per cm2.
It sounds kinda like the “trick” on the internet for fitting more notes onto a note-sheet for an exam. You’re still using the same physical space to store information, but you’re introducing a new degree of freedom that allows you to increase storage density.