no 'bits' in it (sorry forgot the pedants term)
Condensation nucleii. If the air is 'clear' then no mist will form. Fill it full of carbon particles, such a exhaust from the GPU, then the air has something on which to condense.
It is also the same with freezing nucleii. Saturated air temp of -15 with nothing in it, no ice. Stick in an aircraft and there's something nice and big on which to freeze.