I've seen a video or two, but they look like a branch cut-off from a lady in flower and stuck in the soil. I've never seen a real cannabis plant that small, other than an unrooted or freshly-rooted clone.
Years ago on another site, there was a competition to see who could grow a cannabis plant in a shotglass. Was funny watching them try, and a few even did the clone in a cup thing in an attempt to bullshit the membership, but cannabis won't grow like that. You'd have to remove, trim roots and foliage and replace...almost daily. The plant could never recover from the injuries, and will die.