They're trichomes. If they appear on the large leaves, it means your plant is producing a lot of resin.
The trichomes contain terpenes and cannabinoids, giving your plant aroma and potency in its effect. The plant also uses them as a protection mechanism against harmful UV rays.
Cheers.
Nothing to worry about. You can clearly tell in the picture how they are coming directly out of the leaf and they have a perfect sphere on the top. The fan leaves are producing Trichomes which is what we want to smoke. Lol
Hope this helps.