He spent the next ten years in Heidelberg as a researcher at the Max Planck Institute for Nuclear Physics.

In 1994, Grimm applied to the University of Heidelberg to qualify as a professor by receiving the "venia docendi" in experimental physics.

The work of the experimental physicist concentrates on Bose–Einstein condensation of atoms and molecules and on fermionic quantum gases.

[1] In the following year, the team produced the first Bose–Einstein condensate of molecules (simultaneously with Deborah S. Jin's group at JILA, Boulder, Colorado).

Years before, he had won the Gerhard Hess Prize, a new blood stipend of the German Research Foundation (DFG) (1996), and the Silver Medal of the ETH Zurich (1989).