How to define different material properties to different mesh density area in GMSH?

Hi, I am having difficulty with defining different material properties to the different areas in gmsh, In the image attached below, I want that my circles have different material property and matrix (square - circles) should have different material property, and then I want to export the .msh file to fenics to see the different material property behaviour under loading conditions.
Any help regarding the above will be highly appreciated.
Thank You

See Dolfinx discontinous expression - #3 by dokken or
Electromagnetics example — FEniCSx tutorial