The hologram has a million and one uses but one which is appropriate this week is to create a set of Christmas lights which cannot be destroyed by the cat. So far 3D holograms have used a high-power laser which heats a spot in the air until it ionises and glows with a bright blue light. This would be cat proof but would probably ionise the cat, or any small child which touches them.
The Japanese boffins worked out that if you used a really fast laser, a femtosecond laser, that heats a small spot to a high temperature but only for a very short time. This is much safer because the total energy involved is smaller. You can touch sparks without getting burned.
So far the “holograms” are small very small – Christmas tree light sized.
The system could be scaled up and be used in entertainment or in augmented reality systems. If you are thinking of the sort of “hard light” projector that created holograms in Star Trek.