Iridescent clouds..
           ..up really close

Michiel de Boer (site) videoed sunlit ‘steam’ from hot water using a Lumix GH4 camera. The video was in ‘ultra-HD’ with shutter speeds of ~1/1000s. These images are a few individual frames. See below for his entrancing video.

All images ©Michiel de Boer
Steam from a hot cup of coffee is just a mini cloud. It lets us do experiments that are not easy on the big ones in the sky.

Here we see directly that iridescent cloud colours are not the filmy continua they seem. Instead, individual droplets diffract light to send colours to the eye or camera.

Droplets of similar size in small (angular) regions each diffract the same colour towards us. Here we are privileged to see not the droplets – they are much too small – but their individual light. We see stars similarly even though their disks are much too small for our eyes to resolve them.
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Droplets follow air streamlines. First they are stems, they twist upwards to unfold and bloom as aerial flowers.