system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What powers the microchip inside my credit card and the microchips we put in animals as identifiers for vets?

Are they actually “microchips” or is that a misnomer?
gpt
The reader.

For your credit card it's powered through the contacts, if you mean the visible one. For RFID, they're powered wirelessly, which works fine because they only need a really tiny amount of power.

And yes, they're very much microchips and can run complex code. Most RFIDs tend to be simple -- just spit out a serial number or such. That's probably what your cat has. Now your credit card contains a complete processor capable of doing cryptography and participating in a complex protocol.