Stage 1 (N1) – Light Sleep

• Duration: 1–7 minutes

• Description:

Stage 1 is the lightest stage of sleep, occurring as a person first drifts off. The body hasn’t fully relaxed yet, though brain and muscle activity begin to slow with short bursts of movement.

It’s easy to wake someone during this phase, but if left undisturbed, they’ll quickly transition to Stage 2. As the night continues, very little time is spent in Stage 1 after the first cycle.

• Brain Activity:

Light changes in brain waves occur as the mind shifts from Alpha (relaxed wakefulness) to Theta waves (early sleep).

Stage 2 (N2) – Onset of True Sleep

• Duration: 10–25 minutes during the first cycle (longer in later cycles)

• Description:

The body enters a deeper state of relaxation. Body temperature drops, muscles loosen, and both heart rate and breathing slow down.

Eye movements stop, and while brain activity slows overall, there are brief bursts of faster waves called sleep spindles, which help block out external disturbances and protect sleep continuity.

• Significance:

People typically spend about half of their total sleep time in this stage.

Stage 3 (N3) – Deep Sleep / Delta Sleep

• Duration: 20–40 minutes early in the night (shortens in later cycles)

• Description:

Also known as deep sleep or slow-wave sleep (SWS), this is the most restorative stage. Muscle tone, pulse, and breathing rate all decrease significantly.

Brain activity is dominated by Delta waves (0–4 Hz) — the slowest and deepest brain waves.

• Importance:

Deep sleep allows for physical recovery, tissue growth, immune strengthening, and memory consolidation. Even though the brain is less active, this stage contributes to insightful thinking, creativity, and problem-solving.

Most deep sleep occurs in the first half of the night, with shorter N3 periods later as REM stages lengthen.

Stage 4 (REM Sleep) – Dream Stage

• Begins: About 90 minutes after falling asleep

• Duration: Increases with each cycle (up to 45–60 minutes near morning)

• Description:

REM is marked by rapid eye movement, intense brain activity, and temporary muscle paralysis (atonia) — except for the eyes and breathing muscles.

This stage produces the most vivid dreams, as brain activity resembles waking levels.

While dreams can occur in any sleep stage, they are most frequent and lifelike during REM.

• Significance:

REM makes up about 25% of total sleep in adults.

As the night progresses, REM stages lengthen and deep sleep shortens, which is why we often remember dreams from the early morning hours.

Brain Wave States

Brain activity changes throughout sleep, measured in Hertz (Hz) by an EEG (electroencephalogram). Each type of wave is linked to a specific state of consciousness.

The Hypnagogic State

Hypnagogia is the transitional phase between wakefulness and sleep, occurring when Alpha waves fade and Theta waves begin.

During this stage:

• The mind drifts between consciousness and sleep.

• People often experience vivid imagery, sounds, or sensations (known as hypnagogic hallucinations).

• It’s common to feel as if you’re falling or hear your name being called.

• A sudden muscle contraction, called a hypnic jerk, may occur.

Hypnagogia is the gateway to dreams, where awareness can blend with the dream world — a prime entry point for lucid dreaming, reality shifting, and deep meditative states.

When Lucid Dreaming Is Most Likely

As the night progresses:

• REM periods increase

• Deep sleep (N3) decreases

During the early morning hours, REM can last 45–60 minutes, making this the best time for lucid dreaming.

This is often called “prime dream time”, when you can remain conscious while the body stays deeply asleep.

Best Sleep Stages and Brain Waves for Altered States

Lucid Dreaming

⟢ REM sleep: When brain activity is high and vivid dreams occur. The body is paralyzed (atonia) but the mind is alert, combining Theta and light Beta waves.

⟢ Hypnagogic State (Alpha → Theta): By staying conscious as the body falls asleep, known as a Wake-Initiated Lucid Dream (WILD).

Reality Shifting

⟢ Alpha–Theta transitions.

⟢ Hypnagogic State (as you fall asleep).

⟢ Stage 1 (N1) and Stage 2 (N2) sleep.

⟢ REM sleep (especially through lucid dreaming).

⟢ Hypnopompic State: Immediately after waking, when you can slip back inward before full alertness returns.

Void State / Deep Meditation

⟢ Hypnagogic State (before sleep): As you drift from wakefulness (Alpha) into light sleep (Theta), the mind stays aware while the body relaxes. This transition is one of the easiest ways to enter the void; awareness expands into still, black emptiness.

⟢ Stage 1 (N1): The lightest sleep stage with Theta waves. If you remain conscious as your body falls asleep, you can slip directly into the void instead of losing awareness.

⟢ Stage 2 (N2): With deeper Theta activity and minimal movement, this stage can stabilize awareness in darkness and silence if consciousness is maintained.

⟢ REM Sleep (Lucid Dreaming): During vivid dreams, the conscious mind can dissolve the dream scene, leaving only awareness — a direct, vivid entry into the void.

⟢ Hypnopompic State (right after waking): As the brain shifts from Theta to Alpha, staying completely still can draw you back inward into the same still, empty awareness.

Sleep Paralysis

⟢ Between REM sleep and wakefulness (Hypnopompic transition).

⟢ Occasionally during the hypnagogic transition before sleep.

sources:

sleepfoundation.org

andrewholecek.com

Daniel Yetman on healthline.com