Determining the true nature of light has been a complex and enduring quest. Ancient Greeks viewed light as corpuscular, composed of discrete particles. The 18th-century scientists described it as undulatory, or wave-like, a perspective solidified by Maxwell’s electromagnetic theory. Thanks to Planck’s quantum theory and Einstein’s photon model, the current theoretical treatment of light embraces its dual nature, exhibiting both wave-like and particle-like properties depending on how it is observed. On paper, both models are equivalent and can be used interchangeably. Which one to take then to study the interactions of light and arthropods? Both! It is simplicity that will guide our choices. Some aspects of these interactions, such as polarization or interference, are treated and illustrated simply with waves, while others, such as fluorescence, are more clearly understood within the framework of quantum mechanics. When studying vision, we know that a visual pigment that absorbs a photon undergoes a cis-trans transition—the starting point of the vision process is well within the quantum model. However, measuring visual sensitivity to polarization requires the introduction of an electric field, which is a waveform construct.