What Is It? #11

These tiny little disks, digitally enhanced with fall colours, are actually:

A. The surface of a strange piece of metal found at Area 51 (the truth IS out there!)

B. A cross-section of a fiber-optic cable

C. Mineral inclusions in the cell wall of a microscopic plant

D. The fine structure of the enamel in a human tooth

E. Surface features of a red maple leaf