Scientists have won a Nobel Prize for an experiment they did more than 30 years ago. It involved understanding daily habits of fruit flies. Strange as this sounds, it taught us a lot.

What is a body clock? The body clock is also known as the circadianThe term is made up of two Latin words meaning approximately and a day. rhythm, which all living things have. Our body, for example, has certain functions it carries out, such as waking up or going to sleep. Our internal body clock - our circadian rhythm - regulates these daily actions working on a 24-hour cycle for most people. Everyone's circadian cycle can vary a little according to geneticRelating to genes. Each of us has around 20,000 to 25,000 genes. We inherit them from our parents. Although most of our genes are the same as everyone else's, the small differences make us unique. and environmental factors.

What is a Nobel Prize? This prestigiousHighly respected. award was set up by Alfred Nobel, the inventor of dynamite. Troubled by the destruction to life caused by his invention, he left money when he died for a prize to reward achievements that have "the greatest benefit to humankind". The annual prize recognises scientists, writers and those working to promote peace in the world.

So, why is this in the news? This year's first Nobel Prize in Physiology or Medicine has gone to three American scientists for their research on the body clock. Jeffrey C Hall, Michael Rosbash and Michael W Young were given the award because of their pioneering work in the 1980s. They discovered completely new information about the 24-hour biological patterns. The award came as a surprise to the scientists: "You are kidding me," said Rosbash when he found out.

Why 24 hours? There are 24 hours in a day. In parts of the world where there is little daylight, humans still operate in 24-hour cycles. This is because all living things have a circadian rhythm that tunes to Earth's 24-hour rotation.

Why was it a surprise that they won? This category is famous for being hard to predict. The Nobel committee does not usually give the public any clues before hand, but this year was even more of a surprise. This research is quite old. Some had expected that the prize would go to a cutting-edge and more recent research field.

So why did it win? Let's rewind a bit. We have long known that living things have internal clocks. Back in 1729, the French astronomer Jean-Jacques d'Ortous de Mairan found that mimosa plants opened and closed their leaves at the same time each day. They did this even if they were kept in the dark. Something else was making them open and close: their circadian rhythm.

Two centuries later, the Russian-American physiologist Nathaniel Kleitman spent a month living in a dark cave. Again, he woke and slept in roughly 24-hour cycles, even without seeing day and night.

Where do our Nobel prize winners come in? For ages, it was not known how the body clock worked. Then in the 1980s, Hall and Rosbash, and Young (who worked independently) discovered a gene in fruit flies which seemed to control the rhythm.

Over time, they identified a complex web of genes spread across the cells of every living thing. These genes affect each other by releasing proteinsA kind of molecule that drives all biological processes. They make up around one-fifth of our total body mass and without them our bodies could not function. They fold into 3D shapes, making them extraordinarily complicated as a whole. in a cycle that lasts around 24 hours.

So, the body clock is everywhere inside us? Kind of. To understand this, think of a circadian system like the inside of an old-fashioned clock. A network of timepieces and cogs are the genes and proteins. These are regulated and affected by a "primary" clock. This is located in cells in a part of the brain called the hypothalamusA part of your brain which produces chemicals that help regulate your body. These are important because they let you know when your are hungry or thirsty and take care of other important body functions..

These brain cells receive information about light from the eyes. The rest of the body's system responds and adapts to this. For example, lots of artificial light from mobile phones or bedside lamps at night-time can delay your sleep.

In other words, the circadian rhythm is affected by what is inside your body - your genes - and by what is outside your body - things like artificial light or darkness.

Are sleep cycles caused by the body clock? Pretty much. The circadian processes affect how much melatonin is released in the body. Melatonin is a chemical that helps you fall asleep. Our body clock touches on so many genes that our circadian rhythm also affects blood pressure, heart rate, body temperature, metabolismThe chemical processes within the body which produce energy. It derives from a Greek word meaning "change". and even behaviour. "We are truly rhythmic organisms," as Young puts it.

Why is this research so important? Because it can teach us a lot about our health, and the health of plants and animals. If your body clock is temporarily disrupted - because of jet lagWhen you travel to a country with a different time zone you and feel a little muddled or sleepy at the wrong time of day. or a late night - you feel a bit under the weather, but quickly adjust.

If it is always changing - late nights, early nights, lie-ins, early mornings - it can lead to health problems. This is a problem for shift-workers who work in varying patterns, sometimes through the night; sometimes through the day. Unbalanced rhythms have been linked to health problems such as Alzheimer's diseaseA progressive disease that causes brain damage over time. It is a common cause of dementia. , cancer and many more. It is not always understood why.

What are we doing about that? This area of research is called "chronobiology". It could have huge benefits for medicine and public health. It has taught us that some medications are best taken at specific times of day. It has given us the scientific reasons why shift work, or looking at bright screens before bed, is unhealthy. It is used by apps which help you beat jet lag. It has even spurred the debate about whether we should abolish daylight saving time.

The work by Hall, Rosbash and Young may be old, but it is more relevant than ever.

Circadian - The term is made up of two Latin words meaning approximately and a day.

Genetic - Relating to genes. Each of us has around 20,000 to 25,000 genes. We inherit them from our parents. Although most of our genes are the same as everyone else's, the small differences make us unique.

Prestigious - Highly respected.

Proteins - A kind of molecule that drives all biological processes. They make up around one-fifth of our total body mass and without them our bodies could not function. They fold into 3D shapes, making them extraordinarily complicated as a whole.

Hypothalamus - A part of your brain which produces chemicals that help regulate your body. These are important because they let you know when your are hungry or thirsty and take care of other important body functions.

Metabolism - The chemical processes within the body which produce energy. It derives from a Greek word meaning "change".

Jet lag - When you travel to a country with a different time zone you and feel a little muddled or sleepy at the wrong time of day.

Alzheimer's disease - A progressive disease that causes brain damage over time. It is a common cause of dementia.