This Week: Reading magma, predicting giant eruptions
In the News: Pfizer recalls birth-control pills after dosing boo-boo.
Clouds are made of uncountable tiny particles, either water droplets or ice crystals, or a mixture of the two, says Grant Petty, a professor of atmospheric and oceanic sciences at the University of Wisconsin-Madison. “The water droplets are usually about 10-20 micrometers across, or about one-twentieth of the diameter of the period at the end [...]