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NOTE: Another valid option would be to assign a size of 0 to all entities. This would eliminate all the previous size information as well as the information for the mesh, and the default options would become active.
Next, generate the mesh of the volume by choosing Mesh->Generate mesh. Another Auxiliary Window appears into which the size of the volumetric element must be entered. In this example, the value is 1. 
The mesh generated above is composed of tetrahedral elements of four nodes, but GiD also permits the use of hexahedral, eight-nodded structured elements.
We will generate a structured mesh of the volume of the cube. This is done by selecting Mesh->Structured->Volumes->Assign number of divisions to volume lines.
Now select the volume to mesh and press ESC.
Then a window appears where the number of subdivisions for the volume limit lines should be entered.
Enter 10 and click Assign and select one of the lines in X axis, the parallel lines are also selected. Press ESC.
The same window appears again, click Assign and select one of the lines in Y axis, the parallel ones are also selected. Press ESC.
Again click Assign and select one of the lines in Z axis, the parallel ones are also selected. Press ESC.
Click Close when the window appears again.
Then, create again the mesh.
NOTE: GiD only allows the generation of structured meshes of 6-sided volumes.
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