Scale
Re-reading Komarr by Lois McMaster Bujold, and Miles Vorkosigan has just purchased as gifts ear-ring-sized replicas of a few planets, which are apparently "displayed under various levels of magnification, where they proved to be perfectly-mapped replicas of the worlds they represented, right down to the one-metre scale.” A quick calculation suggests that if they're 2cm across, then those one-metre scale objects are less than 2 nanometres across. Never mind "magnification", it would need a high-power electron microscope to see them, which it seems unlikely that the recipients of gifts will have available (although I suppose that in this case one of the recipients is the Emperor of Barrayar, and can presumably get as many electron microscopes as he wants).