Organization of stimuli happens by way of neural processes; this starts with our sensory receptors (touch, taste, smell, sight, and hearing), and is transmitted to our brains, where we organize the information we receive.
Source: Boundless. “Introducing the Perception Process.” Boundless Psychology. Boundless, 20 Aug. 2015. Retrieved 08 Oct. 2015 from https://www.boundless.com/psychology/textbooks/boundless-psychology-textbook/sensation-and-perception-5/introduction-to-perception-39/introducing-the-perception-process-167-12702/