Nylon strings, specifically
classical guitar strings. Created by
Andres Segovia (actually Andrés) during
World War II. He joined forces with a chemical industry family, DuPont, who told him about a material called
nylon. With Segovia play testing and DuPont tweaking the strings they came up with nylon strings. Although,
Albert Augustine created what we all know and love as classical guitar nylon strings. Intersting how a chemical industry during WWII was such a stepping stone in the evolution of what classical guitar is today.
Nylon strings were a huge leap in the classical guitar world. No longer did guitarists have to worry about the inconsistant
density of gut strings (see
gut string guitar). Also nylon strings are far tougher than gut strings.