The spheres are located at each vertex of the cube, and in the center of the faces.[br]The spheres in the vertices contribute with (1/8).[br]The spheres in the faces are cut in half, they contribute with (1/2).[br]There are 8 vertices and 6 faces, therefore there are 4 complete spheres per unit cell.[br][br][br]Versión en español:[br]https://www.geogebra.org/m/fpk7djne[br][br][br]Version in French (by [url=https://www.geogebra.org/u/pantaloni]Vincent Pantaloni[/url]):[br][url=https://www.geogebra.org/m/qyvza9hq]https://www.geogebra.org/m/qyvza9hq[/url][br][br][br]Other structures:[br][br]Crystal structure - simple cubic:[br][url=https://www.geogebra.org/m/rxvmc3uj]https://www.geogebra.org/m/rxvmc3uj[/url][br][br]Crystal structure - body centered cubic:[br][url=https://www.geogebra.org/m/zantmgct]https://www.geogebra.org/m/zantmgct[/url][br][br]