BioSonics is an interactive art installation that explores the transformation of human interaction into spatial and temporal patterns by a dynamical and self-organized system. It both looks at aesthetic qualities of pattern formation processes and explores means of intuitive interaction with complex systems. In BioSonics, users interact with the growth processes of an organism. These processes are controlled by a chemical reaction network whose underlying dynamics eventually leads to changes in the organism’s appearance and behavior. BioSonics produces both visual and acoustic feedback. Each chemical in the system controls its own sound synthesis engine whose acoustic output depends on the characteristics of the chemical, its concentration and its spatial position. Users interact with the organism by means of several microphones. The sounds picked up by the microphones are converted back into chemicals, therefore leading to changes in the dynamics of the chemical reactions and the growth processes they control. By using an acoustic interface, the user’s influence on the system is embedded within the acoustic properties of the environment of which the interactive system as well as other users are a part. Interaction therefore becomes a collaborative endeavor to which the growing organism continually responds by changing its appearance as well as by modifying its acoustic feedback and sensitivity.