Microplastics are fragments of any type of plastic less than five millimeters in length.
Think of larger pieces of plastic that have broken apart - or resin pellets for plastic manufacturing - or those microbeads in health and beauty products.
These tiny particles easily pass through water filtration systems - and they end up in our ecosystem, a potential threat to aquatic life.
The University of Tennessee and TVA are studying the impact of microplastics by examining fish gathered from Tennessee’s watershed.
TVA biologists and university students collected these samples of freshwater fish, dating back to 1965 - now preserved in a collection at UT Knoxville.
The study aims to determine when the microplastics entered the watershed, to measure any effects on the freshwater fish.
Dr. Andreas Fath - a water chemist at Furtwangen University in Germany - is working with the study team.
A few years ago, he strapped a pollution sensor to his wetsuit - and swam the entire 652 miles of the Tennessee River.
I spoke with him - and Dr. Ben Keck, director and curator of the Ichthyological Collection at UT Knoxville.