octahedron in a cube for Kevin's grandma

octa_in_hexa.py

import pyvista as pv

cube = pv.Cube()
# too lazy to define the octahedron manually from cube.cell_centers()
octahedron = cube.cell_centers().delaunay_3d().extract_surface()
points = (cube + octahedron).glyph(geom=pv.Sphere(radius=0.05))

plotter = pv.Plotter()
plotter.theme.smooth_shading = True
# cube lines
plotter.add_mesh(cube.extract_all_edges(), render_lines_as_tubes=True,
                 line_width=5, color='black')
# octahedron surface
plotter.add_mesh(octahedron, color='darkgreen', opacity=0.5, show_edges=True)
# balls for points
plotter.add_mesh(points, render_points_as_spheres=True, color='silver')

# some prettification
plotter.set_background('lightgreen', 'lemonchiffon')
plotter.enable_terrain_style()

plotter.show()

Output: