The ball-and-stick model is a molecular model of a chemical substance in which both the three-dimensional position of the atoms and the bonds between them are displayed.
The German chemist August Wilhelm von Hofmann invented the ball-and-stick model in 1865 in order to better explain the molecular makeup of chemical substances. Initially, he used croquet balls to represent atoms and coloured them differently to distinguish the elements they constituted. As for the bonds, he used metallic tubes and pins. Here is a photograph of Hofmann’s original (albeit incorrect) ball-and-stick model of methane: