Tropism

Tropism is the biological phenomenon that indicates growth or movement of a biological organism (usually a plant) in response to an environmental stimulus.

Photo courtesy of Mark Simmons.

The above tropism is a polarized light microscope image of adipic acid, (CH₂)₄(COOH)₂. The nearly 2.5 billion kg of adipic acid produced each year is mostly used as a monomer for the production of nylon. Other major uses involve polymers. It is a monomer for production of Polyurethane and it is used in making PVC. The image above was captured using a microscope digital camera adapter and a standard digital camera.