In the Bible, it is said that manna, a flaky white substance, fell from heaven every
night as the Israelites crossed the desert. By collecting it and baking it into bread,
they could keep themselves from starving to death. One theory for this occurrence says
that it was the sweet excretion of insects that feed on regional tamarisk trees. Another
states that manna was a form of lichen that was airborne by warm winds and then deposited
on the sand at night when temperatures dropped.