The hard facts about an issue known as 'morning wood'

Morning wood.

The medical term for it is nocturnal penile tumescence, and there's some pretty interesting science behind it.

It has everything to do with our sleep cycle...

...which is why you may have noticed it can happen several times throughout the night.

Sleep happens in stages, stepping us gradually down into deep sleep, which is followed by a spike into shallower rapid eye movement (REM) sleep — the dream stage.

During REM, our brains slow the release of chemicals called neurotransmitters.

It's how the brain regulates our automatic body functions. It also keeps us from doing stuff like unconsciously attempting to act out our dreams.

One of those neurotransmitters — norepinephrine — plays a role in restricting blood flow.

During REM, norepinephrine becomes less active, which opens up blood vessels and increases circulation throughout our body — including to the penis.

The extra blood flow means more oxygen for all parts of our bodies, which is important for standard maintenance and repair.

Erections occur in the mornings because we often wake up just out of REM.

Full bladders may also cause morning wood.

The increased size of the bladder can stimulate a part of the spinal cord that causes a reflex erection to prevent urination during sleep.

So no need to be confused...

or freaked out...

or angry about it.

Because it's just our physiology.

Watch the full explainer below:


If the past year has taught us nothing else, it's that sending love out into the world through selfless acts of kindness can have a positive ripple effect on people and communities. People all over the United States seemed to have gotten the message — 71% of those surveyed by the World Giving Index helped a stranger in need in 2020. A nonprofit survey found 90% helped others by running errands, calling, texting and sending care packages. Many people needed a boost last year in one way or another and obliging good neighbors heeded the call over and over again — and continue to make a positive impact through their actions in this new year.

Upworthy and P&G Good Everyday wanted to help keep kindness going strong, so they partnered up to create the Lead with Love Fund. The fund awards do-gooders in communities around the country with grants to help them continue on with their unique missions. Hundreds of nominations came pouring in and five winners were selected based on three criteria: the impact of action, uniqueness, and "Upworthy-ness" of their story.

Here's a look at the five winners:

Edith Ornelas, co-creator of Mariposas Collective in Memphis, Tenn.

Edith Ornelas has a deep-rooted connection to the asylum-seeking immigrant families she brings food and supplies to families in Memphis, Tenn. She was born in Jalisco, Mexico, and immigrated to the United States when she was 7 years old with her parents and sister. Edith grew up in Chicago, then moved to Memphis in 2016, where she quickly realized how few community programs existed for immigrants. Two years later, she helped create Mariposas Collective, which initially aimed to help families who had just been released from detention centers and were seeking asylum. The collective started out small but has since grown to approximately 400 volunteers.