While they are indeed beautiful, I didn’t see nay snowflakes melting, and I can’t help but wonder just where he found snowflakes forming that were so stationary that he could take time lapse images of them.....
Do you know what a "cloud chamber" is?
It's a closed container which gets filled with a mixture of air and water vapor at nearly one-hundred percent humidity; that is, the air can't hold any more water vapor without the water condensing out.
The container is made so that the volume of the container can be increased. This lowers the pressure and results in air which is then super-saturated; that is the humidity is actually above one hundred percent. The slightest disturbance in the air will trigger condensation of the water creating clouds.
Cloud chambers have been used in scientific studies of atomic particles. The particles passing through the chamber act as the disturbance and cloud tracks are created showing the passage of the particle.
I would guess that the apparatus used for the video has similarities to a cloud chamber. The conditions are set to encourage formation of snowflakes and the snowflakes will form around particles which disturb the conditions.
One trick to make the snowflakes stationary might be to perform the experiment in outer space where there is no gravity. Jets in a steep dive can mimic a zero gravity condition for a minute or so. It is a pretty neat trick.
The experiment would rely on having just the right temperature, pressure, humidity, and the presence of minute dust particles perhaps to form the nucleus for the snowflake. Possibly the nuclei can form just on what particles exist without purposely introducing them.
Another requirement is to use a light source for illumination which doesn't heat the snowflake and disturb its growth.