Most people, when they go to bed, aim to sleep until the morning but some wake up and are active in the middle of the night.
Last week, we published a story about the myth that an eight-hour sleep is necessary for good health. In response, 10 people told us how they sleep in two separate chunks and what they do in between.
Take photos of the city Brennan Wenck-Reilly, 36, San Francisco, US
I spent two years living high in the Andes in a town that had no electricity where I went to sleep and rose with the sun. Now I naturally wake around 01:00 or 02:00 and then become tired again around 03:00 and sleep until 07:00 or so.
My friends have always made fun of my sleep pattern and my wife used to force me to get out of bed as my lying there would disturb her.
I’ve decided to use this time creatively and run around San Francisco taking pictures in the night. We just had a small storm pass through the city, so there are some cool clouds in the sky. I have been itching to go out.
Late night yoga Annelieke Dirks, 33, Amsterdam, The Netherlands
I wake up at about 04:00 every night to practise yoga.
Most of the time I do it at home, but once a week I drive to a yoga studio in Amsterdam where I practise with about 20 other people.
I teach and practise kundalini yoga, which has followers all over the world who live in a similar rhythm.
I go back to sleep but some people don’t. I find a lot of yogis don’t sleep very much.
Sometimes, my partner joins me, if he’s having trouble sleeping, but mostly he just sleeps through it.
I used to sleep eight or nine hours a night and still always felt tired. But I’ve never felt so good in my life as I do now.
Draw pictures Carolyn Cornell, 78, Austin, Texas, US
As an artist, many of my paintings have come directly from my dreams.
I usually wake up around 03:00 and sometimes I have such a strong image in my head that I have to grab a piece of paper and draw it immediately.
I trained as an art therapist and used to work with a young boy called Jonathan who had cancer. He was writing a cartoon story and we were working to put it together when he had a bad relapse and died.
Afterwards I dreamt about him and one night I woke up with a vivid picture of his face. Above it was a speech bubble filled with different colours.
I drew the image immediately and later made this painting of him.
Muslim prayers Reham Samir, 25, Cairo, Egypt
As a Muslim, I get up to pray in the middle of the night.
We are advised to sleep and then wake up in the third stage of the night before sunrise, though this night-time prayer is voluntary. It’s called Tahajjud, the Arabic word for night prayer.
I usually get up and pray alone rather than going to the mosque. We also have a dawn prayer, which is obligatory, so sometimes I stay up until dawn and then go back to sleep.
According to the Koran, Muhammad slept in this way. So segmented sleep is quite normal in the Muslim tradition.
Play with friends in the tribe Iain Wilson, 37, Papua, Indonesia
I grew up among the Yali people in Papua, Indonesia. When I was born, my parents lived in a remote area. My mother was a medical worker and my father was an anthropologist. We lived there until I was 16, and as a child I used to camp and go hunting with my friends in the Yali tribe.
When I stayed with them, we would go to bed more or less after sunset and people would always wake up during the night.
I would hear them talking and someone would start a fire. Sometimes we would eat some sweet potato before going back to sleep until 05:30 or 06:00.
At home with my parents, I would get a regular eight-hour sleep, but when I was with my friends, I slept like they did.