They may be beautiful, but that beauty is, in one sense, a burden. When and how flowering plants began has long been one of botany's biggest and most beautiful mysteries.

SUN GE (Paleobotanist, Jilin University): Fossils form in between the layers of sediment. An enclosed seed is a defining feature of a flower, today. After months of analysis, Sun Ge decided to share it with a fellow botanist in the United States. NARRATOR: Dilcher is one of the world's leading paleobotanists, which is the study of ancient plants and their fossils.

Searching for fossils is like opening the pages of a book. NARRATOR: Sun Ge searched for more than a decade, through these layers of rock, without success. This priceless fossil, that had been buried deep in the earth for more than a hundred million years, had to endure one more burial in another kind of tomb. His passion is trying to understand the origin of flowers.

So subsequently the Last Word posed a second question.

Does any reader know why alternating blades makes each one last longer?

One of the best places on Earth to see the results of the evolution of flowering plants is the Hengduan Mountains in southwestern China, which span the regions of Sichuan, Hunan and Tibet. Lilium lophophorum—it's the first time I've seen it in flower. One of the things that make the Hengduan Mountains such a rich breeding ground for plant life is the variety of climates.

This is the most biodiverse temperate forest in the world. The petals don't completely dis-attach which makes it so exquisite. They like to say, here, that you can experience all four seasons in one day.

Why do I, or any other human, get sore and cracked heels?

I understand it's less common in men than women – presumably this is down to footwear choices?

One day a student dropped off three new fossils at his office. Sun Ge brought the fossil to his longtime friend and colleague David Dilcher, of the University of Florida, for another opinion. DAVID DILCHER: I've been looking for the earliest flowering plant in the world for, probably, 35 years.