This is an old video of two identical smoke rings colliding, or, in more scientific terms, "a head-on collision of colored vortex rings. Note the formation of small rings from the cross-linking of the wavy vortex filaments of the larger rings." So basically this steamy video has it all: colored vortex rings, cross-linking, wavy vortex filaments -- you name it. I swear, if this clip were any more erotic you'd have to rent it from the curtained section of a video store. PROTIP: wear a trench coat and fake mustache.
Keep going for the whole video. Also, what's up with the video shake when they collide? Just how powerful was this?
Thanks to Randi, who informed me Gandalf did it first.