In the hands of an occupational hygienist, the combination of light and a fluid medium is a scientific tool to demonstrate the flow of vapours, the way aerosols hang suspended in the air, tiny particles that linger and drift, hovering like miasmas. When the gaseous medium of air is freighted with moisture, light makes air visible, revealing it as dense and saturated. This sudden revelation brings into sharp relief the normally unseen residues that we share with those around us each time we breathe and speak – potentially lethal fluid vectors of contamination. However, if we step back from the anxiety this revelation might induce, we can see this demonstration as a key to understanding how an encounter between linear streams of light and meandering fractals of a fluid medium is at the core of some of the most exquisite and enlivening aesthetic experiences in contemporary culture.