Clouds

And now, from The World of Order and Organization, the classification of clouds.

High-level (3 - 8 miles)
   cirrus: light, fleecy
   cirrocumulus
   cirrostratus
   (also noctilescent: (glowing atmospheric methane at 50,000 feet))

Middle-level (1.25 - 4.3 miles)
   altocumulus
   altostratus
   nimbostratus

Low-level (0 - 1.25 miles)
   stratocumulus
   stratus: horizontal, misty
   cumulus
   cumulonimbus