Walther Hesse is best known for his work in microbiology, specifically his work with his wife Fanny Hesse in developing agar as a medium for culturing microorganisms.

Fanny Hesse is best known for her work in microbiology alongside her husband, Walther Hesse. Following her initial suggestion of using agar as an alternative to gelatin, they were instrumental in pioneering agar's usage as a common gelling agent for producing media capable of culturing microorganisms at high temperatures.