Cotton is an ancient fiber which is used by people for many things. What is its original function for the cotton plant?

This is Oak Tree House at Mesa Verde National Park, built by Native Americans in the year 1250 A.D. They left no written records, and no verbal history survived, so how do we know so precisely when it was built?

What is this, and is it edible?

The itching rash caused by Poison Ivy, Poison Oak, and other related plants is caused by a substance called urushiol. What function does urushiol serve in these plants?

While driving home from town, we noticed that some of the plants along the road were covered with what looked like yellow string. What is it?