Do you know what is mean't by Persistance of Vision? If you don't thats ok. It has to do with the way our eyes see things and brain interprets those visions..
What happens is, even if an even has passed,you eyes might still see it, for e.g. stare at a light, if you close it, it might seem that its taking its sweet time to close.
Its actually more apparent when you look at a high speed fan.. Even though the blades are not everywhere at the same time, you do see them slightly. You can't tell exactly where which blade is/was. It takes a little while for our eyes and brain to register a sight. And it can remain there for some milliseconds even after it has gone. This technique if used to create films and movies (which is basically 30 still images or more per second, but to our eyes, it looks like its moving).
Similarly, some people made fans that displayed a message when it spun. For e.g., see the below image
It seems that the message is written on air, but in reality, its not. Its on the fan blades (which changes LEDs based on where they are at that exact moment in time).
This is the same concept that has been used in these new 3D holographic fans (or devices you can say). Check the main video above.
Now that device is not a novelty anymore. You can get it for fun, or maybe perhaps you have a display shop or mall. Or maybe you would like to display your product somewhere nice. These used to cost in the thousands, but now you can get it for less than $400 from http://bit.ly/3Dholograms - The device comes like this:
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For more information, and the science behind it, you can visit New Realistic Hologram Machines From China – Persistance Of Vision
Have fun, and if you do get it, do upload your videos and show us what you do with them!