In the species panel you assign the physical material properties to an object as they have been defined in the Physics Module.

Since several types of materials may spatially coincide, you can assign more than one species with different physical properties.

All the species that have been defined in the Physics Module appear in the drop-down menu. After you choose a species, press the Add button to add this species to the list. To remove a species, select it on the list and click on the Remove button.