The word "hologram" is being used a lot nowadays, referring to everything from Pepper's Ghosts (the ancient visual effects that have been resurrected recently to create the illusion that a deceased celebrity is on stage) to virtual and augmented reality images. But a true hologram is a lot more impressive than that, it's nearly indistinguishable from the real object, even when they're side-by-side. Here's a lovely example from an exhibition in St. Petersburg, Russia, from several years ago. The reason we don't see more of these is that there's an incredible amount of information involved even for the best currently available processing and storage techniques (since the pixels are the size of the wavelength of visible light, which means smaller than a thousandth of a millimeter). But if you're fortunate enough to be in a place like NYC or Boston where there are often holograms on public display, they're worth going out of your way to experience.