Many stars of the past are being brought back to the big screen using advanced vfx techniques. This was seen most recently in "Rogue One: A Star Wars Story". Peter Cushing reprised his role as Grand Moff Tarkin, which he first played in 1977. This wasn't easy to do considering he dies in 1994!
Visual effects has always had a big part in film but usually with more obvious effects such as explosions, space travel or even dinosaurs. The possibilities with this technology are now close to endless as companies like Lola VFX continue to perfect their art.
Read about it in more detail on this article by New York Post: