The 15x20 micrometres card requires a powerful microscope just to see it, let alone read the festive message inside.
Created by researchers at the National Physical Laboratory (NPL) in the UK, it features a whimsical, jolly snowman and the words 'Season's Greetings'.
The card is made from platinum-coated silicon nitride, usually used in electronics, and both the design on the front and the message inside were carved out by a focused ion beam - a jet of charged particles.
The tools used to make the card are being used to develop cutting-edge techniques for understanding materials on a tiny scale, helping to further the miniaturisation of electronics, and the development of new battery materials.
"We are using the tools that created the card to accurately measure the thickness of extremely small features in materials, helping to unlock new battery and semiconductor technologies," Mr Cox said.
"It's a genuinely exciting development that could help to make new technologies and techniques a reality," he said. NPL's card is 10 times smaller than the previous record- holder.