At an early stage of learning quantum chemistry, undergraduate students usually encounter the concepts of the particle in a box, the harmonic oscillator, and then the particle on a sphere. Rotational levels of a diatomic molecule can be well approximated by the energy levels of the particle on a sphere. Wave functions for the particle in a one-dimensional box and the one-dimensional harmonic oscillator are functions of one coordinate and are easily drawn using Microsoft Excel due to rapid advancements in computer hardware and software. In this article, wave functions for rotating diatomic molecules (spherical harmonics) were three-dimensionally visualized by using Graph-R in tandem with Excel. (Contains 2 figures.)