Mag stripe. The back of your credit cards. Probably your driver's license as well.
That mag stripe back there is, more or less, a hard drive, or at least a pre-set group of characters that identify you electronically, usually with lots and lots of numbers.
The mag stripe technology is not new; it's been around since the mid-1970s and was simply refined like 897 times along the way. The data used to get erased if you looked at the stripe sideways. Or held it within 8 miles of a magnet. Or stood in a county where there were lightning strikes. Over time, the stripe got "bigger," i.e., and held more data. It got more stable, and it got ubiquitous.
Most pediatricians and workers at Microsoft believe that, after 2032, over half of babies born will have a mag stripe embedded in their left foot. (Great for field goal kickers, at least.)