Information on compact discs (CDs) is stored by a binary pattern of real physical holes in the plastic surface just below the reflective aluminum foil. During recording (or 'burning') a CD these holes are literally burned in the plastic by the laser in the CD/DVD players in our PCs and laptops.
スキャン BudgetSensors Tap300-G
AFM probe, 25 micron scan size
Image courtesy of Dr. Yordan Stefanov ISB, Bulgaria