This Element introduces a biological approach to cognition, which highlights the significance of allostatic regulation and the navigation of challenges and opportunities. It argues that cognition is best understood as a juggling act, which reflects numerous ongoing attempts to minimize disruptions while prioritizing the sources of information that are necessary to satisfy social and biological needs; and it provides a characterization of the architectural constraints, neurotransmitters, and affective states that shape visual perception, as well as the regulatory capacities that sustain flexible patterns of thought and behavior.