Xander is sleeping. His eyelids are quivering because his eyes are darting around. Xander is probably experiencing what kind of sleep

Answer;

REM sleep

Xander is probably experiencing REM sleep.

Explanation;

-REM sleep is a stage of sleep that is characterized by low muscle tone, rapid eye movements and dreams. It is present in all mammals and has unique physiologic properties that distinguish it from non-REM sleep.

-It is believed that the chemical and electrical activity that regulate this sleep phase originate in the brain stem, and this is most notably characterized by a combination of an abundance of acetylcholine (a neurotransmitter), and the almost complete absence of serotonin, histamine, and norepinephrine.