Students become deeply involved in physics classes when spectacular demonstrations take over from abstract and formal presentations. In this paper we propose a simple experimental setup in which the wave behavior of light can be made spectacularly evident along the whole path of the light beam in a practically unlimited number of configurations. The idea is simply that of adopting a fog-making machine to show, by means of light scattering along its path, that diffraction and interference are effective processes, i.e., they do not "switch on" just at the detection screen, as one could somehow be tempted to imagine in a more conventional setup. In our experiment, an ultrasonic mist maker is used to produce a small, homogeneous volume of water vapor fog (see Fig. 1). The fog is produced through water fragmentation caused by the mechanical action of a ceramic electrode that oscillates at ultrasonic frequency.