In this Chalkboard article, the conceptual basis of fluctuation analysis, also known as noise analysis, is discussed from an electrochemist's point-of-view. While both impedance spectroscopy and fluctuation analysis can provide similar information about an electrochemical system (e.g., charge-transfer resistance and double-layer capacitance), the advantages of the latter are emphasized here. Specifically, fluctuation analysis allows the system to be studied at true thermodynamic equilibrium without external perturbation. The origins of the spontaneous and stochastic fluctuations observed in electrochemical systems and solid-state devices are associated with the four common “flavors” of noise—thermal noise, shot noise, excess noise, and work function noise. The information obtainable from each of these, and the systems they're most commonly applied to, are briefly outlined.