Let us never underestimate just how far special effects have come in films. And if you're still a non-believer, maybe the pictures below will change your mind.

Twitter user @thisbemesara has been sharing some brilliant images from film sets that show just how much computer-generated work goes into the finished product - and how on earth actors manage to keep straight faces while faced with people in green leotards and generally acting around green screen backgrounds.

Some of the best ones are from the likes of Alice in Wonderland, The Life of Pi and Guardians of the Galaxy, as you'll see below: