The National Physical Laboratory has made the world's smallest Christmas card using ion beams. It's about 200 million times smaller than a stamp, and you could fit 7 quadrillion in a post box. https://t.co/vfRAdIwejG https://video.twimg.com/ext_tw_video/1787187662731747328/pu/vid/avc1/926x598/zNkAtAu2V9UqLZMa.mp4?tag=12