The DSM-5-TR notes that autistic people can have hyper- and hypo-reactivity to sensory input – also called over- or under-responsivity, hyper- or hypo-sensitivity. They can also have an unusual interest in sensory aspects of the environment, which may include sensory craving. In this chapter, readers learn about the five senses everyone knows (hearing, touch, vision, taste, and smell), as well as proprioception (information about body position and movement), vestibular information (about the position and motion of the head and body), and interoception (internal bodily sensations), and how these senses are integrated. Over-responsivity (also called sensory sensitivity or sensory defensiveness) can lead to extreme discomfort or reactions to any of these sensations. Under-responsivity occurs when an individual shows little to no response to external stimuli or to internal sensations. Many autistic people also report other unusual sensory experiences, such as synesthesia and misophonia. Sensory differences often change over time and can have an overwhelming impact on an autistic person’s ability to function.