Another method is to use a high-powered pulsed laser to create little balls of plasma in mid-air: https://www.popsci.com/secret-interactive-holograms-plasma-and

Another method is to use a high-powered pulsed laser to create little balls of plasma in mid-air: https://www.popsci.com/secret-interactive-holograms-plasma-and-femtosecond-laser https://www.popsci.com/secret-interactive-holograms-plasma-a...