This is a sequence of animations broken into six parts on the Stages of Sleep.

1. Part 1 of 6: An animated diagram of the stages of sleep is shown.
2. The on-screen text says "During sleep, people cycle through a series of four distinct stages. As you descend through stages 1, 2, and 3 of the sleep cycle, your respiration rate, heart rate, muscle tension, and body temperature gradually decline."
3. Part 2 of 6: An animated diagram of the stages of sleep is shown. Below the diagram, an animation of sleep-related brain waves is shown.
4. The on-screen text says "Stage 1 is a brief transitional stage of light sleep in which theta waves are prominent. Stage 2 consists of light sleep and typically lasts about 10–25 minutes. Gradually, your brain waves become higher in amplitude and slower in frequency as you move into stage 3. Stage 3 is a deep form of sleep that is called slow-wave sleep because low-frequency delta waves become prominent."
5. Part 3 of 6: An animated diagram of the stages of sleep is shown.
6. The on-screen text says "After 20–40 minutes in slow-wave sleep, the sleep cycle reverses itself, and you gradually move upward through the lighter stages of sleep. When you reach what should be stage 1 once again, you usually go into the fourth stage of sleep. This stage is known as REM sleep. REM is the abbreviation for rapid eye movements, which occur beneath one’s closed eyelids during this stage."
7. Part 4 of 6: An animated diagram of the stages of sleep is shown. Below the diagram, an animation of REM sleep beta waves is shown. Then, these images are removed and two pie graphs shows the ratio of dreams recalled during awakenings for REM and non-REM sleep are shown.
8. The on-screen text says "Although REM sleep is a deep stage of sleep in that it is relatively hard to awaken a person, EEG activity is dominated by high-frequency beta waves that resemble those observed when people are alert and awake. REM sleep is also the stage during which most dreaming occurs. In lab studies, REM awakenings produce dream recall about 75% of the time, whereas awakenings from other stages are accompanied by dream recall only about 15% of the time. REM sleep is such a special stage of sleep that the other three stages are often characterized as non-REM sleep."
9. Part 5 of 6: An animated diagram of the stages of sleep is shown.
10. The on-screen text says "During the course of a night, people usually repeat the sleep cycle about four times. As the night wears on, the cycle changes gradually. The first REM period is relatively short. Subsequent REM periods get progressively longer, peaking at around 40–60 minutes. Additionally, non-REM intervals tend to get shorter and descents into non-REM sleep become shallower."
11. Part 6 of 6: An animated diagram of the stages of sleep is shown. Then, the diagram is removed and a pie graph summarizing the ratio of time spent in each sleep stage during the night is shown.
12. The on-screen text says "These trends mean that most slow-wave sleep occurs early in the sleep cycle and that REM sleep and dreaming tend dominate the second half of the sleep cycle. Summing across the entire cycle, young adults average about 6% of their sleep time in stage 1, 48% in stage 2, 20% in slow-wave sleep, 22% in REM sleep, and 4% of their time awake."
13. End of animated sequence.