Space-filling models (also known as calotte models or CPK models^[1] by Corey, Pauling and Koltun), like ball-and-stick models, belong to the 3D or spatial molecular models, which serve to display the structure of chemical products and substances or biomolecules.

The calotte model is a further development of the ball-and-stick model, with which the configuration of molecules can be vividly presented. With it, the atoms of individual elements are represented by multicolored spherical sections. Atom size, bond angle and bond length correspond to the actual relationships. The result is a clear and (depending on construction materials and execution) flexible model of the molecule. Presentation is also possible using software.