Appropriate grades or age groups:
6th grade and up

Estimated time to complete this project:
A couple of weeks or up to a month.

Materials:
1) 3 slices of bread
2) water
3) places to put the bread
-in the dark
-in the light
-in between light and dark

Instructions:
Dampen the 3 slices of bread with water.
Put one of the bread slices in a dark place, the second in a place that has light, and place the last slice in a place where it's between light and dark.

Other comments or suggestions:
Don't wet the bread too much because it will take longer.