The microscopic remains of dozens of prisoners, most of them women, who were executed for resisting Adolf Hitler and whose bodies were used for research by Nazi doctors, were buried in a simple wooden box at a Berlin cemetery on Monday.

A plaque that tells of the victims’ fate will be placed over the grave, in Dorotheenstadt cemetery, where other victims of the Nazis are also buried. The cemetery is several blocks behind the Charité, Berlin’s main research hospital.

The fragments of the prisoners’ remains were given to the hospital two years ago by the descendants of Hermann Stieve, a doctor who made a deal with the Nazis to obtain the remains of the prisoners for research. They had been killed at the Plötzensee prison, which is in western Berlin.

The fragments were contained on 300 glass microscope slides, each only a hundredth of a millimeter thick and roughly a square inch in size.