This chapter presents numerical analyses performed on real physiological systems, focusing on the characterization of their intrinsic informative noise under various pathophysiological and experimental conditions. Each section is dedicated to the analysis of a specific physiological system, covering both cardiovascular and neural systems across different spatial scales. For each case, the real-world datasets are introduced along with a description of the experimental setup, followed by the presentation of the corresponding numerical analyses. Physiological noise in the cardiovascular system is investigated using heart rate variability (HRV) series. The neural system is studied across multiple scales—ranging from single-neuron activity, assessed via invasive electrode recordings and calcium imaging, to cortical and whole-brain dynamics explored through noninvasive techniques such as electroencephalography (EEG) and functional magnetic resonance imaging (fMRI).