How do you make these? I have saw a lot of people doing it on twitter?

[Amy]

https://www.google.co.uk/search?q=heart+...=356#i=127

[Katie]

You would have to have a professional camera and then you use shutter speed in dark room. I usually set it for a slow shutter speed so it can catch the image, just experiment. You then need a torch to draw the heart shape.

[Rick]

You need to be in a very low light situation. Then you put your camera on something very stable, like a tripod. You need to have a camera that lets you keep your shutter open for an extended time, say 5-10 seconds. If you have "B" on your camera then the shutter stays open as long as you hold the button in that mode. Hold your shutter open and draw what you want with any source of strong light. That can be anything from a lighter to a torch. Check your exposure and adjust your aperture accordingly. Try f5.6 to start.