He served as director of the Physics Department at the University of Marburg for 20 years, and was editor of Annalen der Physik together with Max Planck.

[1][3][4] After graduating from a humanistic gymnasium in the spring of 1895,[1] he at age 17 was drawn to pursuing natural sciences, which was the only area not represented among his brothers.

[1] In 1933 Grüneisen signed the Vow of allegiance of the Professors of the German Universities and High-Schools to Adolf Hitler and the National Socialistic State.

[1] During the Third Reich, Grüneisen refused to begin his lectures with the Hitler salute, and he sometimes expelled Nazi-leaning students from the laboratory.

Notably, he took on Henry H. Barschall as a doctoral student for as long as he could and ultimately helped him emigrate to the USA.