How small could intelligent aliens be?

[TimeFlipper]

And they have tiny space ships too? That could be amazing....wonder what size of planets they are from...gravity level etc...

You reminded me of an episode of the Twilight Zone, where a scientist is in radio contact with some aliens in a UFO..the occupants have an electrical problem in their craft and they crash into a field very close to where the scientist is....He races out to try and help them but unknowingly steps onto their craft which was the size of a golf ball...I never did understand the moral behind that episode

Maybe they should have shouted, 4!