Mike Springer Homeostasis is an essential and ubiquitous theme in biology. Biological molecules often need to be maintained in narrow concentration ranges. Multiple different homeostatic networks share a similar basic design including an internal sensor and a regulated high affinity transporter. This network wiring can be described by two coupled differential equations. The solution to this equation is the same as the solution to a damped harmonic oscillator (from physics) or proportional integral control system (from electrical engineering). This design allows maintenance of a constant internal concentration of nutrient even if external nutrient levels, uptake, or other kinetic parameters vary. While maintaining homeostasis, this simple system can be energetically costly and kinetically slow. As seen in many of the systems, additions such as low affinity transporters, nutrient dependent usage rates and buffering can work to decrease the energy and time required to reach and maintain steady-state levels of nutrient. While robust to many parameters, this system is evolvable and noise in the system allows for individuals to have different thresholds of response in an isogenic population.