Edit: Ah, I see, it's the Tupac hologram. 2D visual on material, 3D effect. Kind of like how 3D in an IMAX isn't the kind of 3D we're thinking of for this.
A hologram is essentially a photographic recording of a field of light waves that are echoed off of an object with lasers. By shining this echoed light onto photographic emulsion in combination with a second laser light, an interference pattern is encoded on the film. When you look at a hologram under a light source, the image you see is that interference pattern being reproduced.
...the Holocaust is unique in historic example for one simple reason. It was the coldest, most systematic and straight business like approach to the extermination of human life ever seen in history, on anything approaching that scale. It wasn't even done in anger. Just cold process.
Intake, Evaluate, Assign specific value then either liquidate immediately or work to breaking. Depends on the evaluation stage. Some even served as medical experiments instead. Yes, everyone had a role in that "system" and "machine". That systematic nature, like nothing else ever seen before or since, is what I think will always have it in a VERY special distinction, all it's own.