How do you make a crystal?

Question

I seen it on some bill nye video.

Answer 1

You grow them.

A nucleation point (String on a pencil hanging over a bowl of -) in a gas of 'salt vapor(s)' (- Salt water) will grow salt crystals. (under the right conditions - humidity etc.)

NaCl - Sodium Chloride.

Answer 2

put water in the freezer