Have you ever experienced the feeling of falling as you start to fall asleep? Sometimes you may come to realize this feeling. If so, don't worry. Many people have felt the same thing.

In fact, these muscle twitches (肌肉抽搐) in the arms, legs or other parts of the body are called hypnic jerks (入睡抽动) or sleep starts. And they are very common. Up to 70 percent of people experience them sometimes, Huffington Post reported. But what causes it?

There are some theories(理论). Some scientists believe that the feeling of falling comes from the body relaxing itself, especially if the person is anxious or unable to get comfortable. As you're about to sleep, your muscles become relaxed. But your brain stays awake. It misunderstands the relaxing of your muscles as a sign that you're falling. Then the brain jerks the body awake as if it's trying to protect you.

    Other scientists believe that different phases of sleep might cause the hypnic jerks. When we sleep, we experience two phases: non-rapid eye movement (NREM) and rapid eye movement (REM). During REM, our heart rate (心率), breathing and nervous system can act irregularly (不规律地). If the body experiences flashes (一瞬间) of REM while entering sleep, these irregularities could cause twitches.

If you don't want to experience hypnic jerks, scientists have some suggestions. When you become deeply relaxed, you can learn how to reconnect slowly by moving your fingers and toes a little bit. Then start to move your head and open your eyes, while being aware of yourself as you get out of the relaxed state.

    But experts agree that hypnic jerks, though sometimes scary, are harmless. If it wakes you up, simply roll over and go back to sleep. But keep in mind: a caffeinated (含咖啡因的) drink, exciting evening activities or stress may make hypnic jerks happen more often.

Surprising Camara.

    WATCH out! A slingshot(弹弓) is aimed at you. But don't be afraid. It's just a camara. It's called Slingshot Camara. The camara will catch your Surprised look. Pull the rubberhand(橡皮筋)back and shoot. It takes a Picture. Two designers from South Korea made's.

Making Use of Smog

    SMOG(雾霾)is annoying. But what if it could be made into a diamond(钻石)? A “Smog Free Tower” will try to do that, although the diamonds will not be as real ones. Black particles(颗粒)in smog and diamonds are mostly carbon. A designer from the Netherlands made the tower.

New Flower Home

    WHEN plants get too big, you have to move them from a small flowerpot to a big one. Now, the special Growth Flowerpot can save you time and energy. It's made of a special materal in origami style. It gets bigger and bigger as the plant grows. It is from Belgium.

Easy Bike Parking

    PARKING a bike is not easy in big cities. Here comes the bicycle-parking tower. You only need to use a card and push a button. Then the tower can hold your bike in an empty place inside it. You don't even need to lock the bike.

Solar Charged Light

    YOU can put it in your pocket. But if it's inflated(充气), it turns into a light! This is LumnAID, a solar light that can be on for 16 hours after recharging(充电) with just seven hours of sunlight. Two US students designed it.

    Do you know kind words and light music can help plants grow better? Many people talk and play music to their plants. And many people try very hard to protect their plants from loud noise, strong light and bad smell. That's not all. Some people are very careful about what they say or do in front of plants. They don't talk about unhappy things and won't beat a fly near their plants.

    Do plants have feelings? Many pupils think so. Even a few scientists think that plants have feelings. But most scientists don't agree. They don't think that plants call be happy, worried, angry, loving or afraid. They don't believe that a plant's feeling can be hurt.

    Professor Cleve Backster in America did an experiment and said that plants have feelings like human beings. He published an article in a magazine in 1968. People began to pay more attention to this topic since then.

    Today, many endangered animals live in zoos. There, scientists work to keep each species(物种) alive. How do they do that? One way is by taking cells(细胞) from animals. Then the cells are frozen(冷冻). They can be used in the future to help animals reproduce.

    The San Diego Zoo has been freezing cells for 40 years. It's also called the Frozen Zoo. Now, the zoo is the biggest of its kind, with a large gene bank. It has cells from more than 1,000 species. One of the species is the northern white rhinoceros(犀牛).

    There are only five northern white rhinoceros alive in the world now. They are unable to have their children. Some scientists there want to use the bank's frozen cells to produce another northern white rhinoceros. They want to do this before the species dies out. That could happen by 2025.

    Can the zoo save the northern white rhinoceros? Other species have been saved successfully. So it's possible for the white rhinoceros too.

    Saving the white rhinoceros would be expensive. So some people don't think using frozen cells is the best thing to do. Some wonder whether it's worth spending millions of dollars on the species that nearly dies out. Some say scientists should work on the reasons why animals become endangered in the first place.

    Mobile phones are very popular with people. They are becoming smaller and more convenient.

    Now the scientists in Canada made a smart phone (智能手机)from electronic paper. The Paper Phone is flexible. People can control it by bending it or writing on it with a pen.

    Though the Paper Phone is only millimeters (毫米)thick, people can do many things with it. For example, people can use it to make phone calls, read books, watch movies and play music. So many people use it as a computer.

    The scientists think there will be no paper in the office. And people can store what they want in the Paper Phone.

    The scientists from Queen's University in Kingston, Canada said the Paper Phone would be in style in the future. It may be the end of paper and printers.

    To make people be interested in this kind of mobile phones, the scientists will make it more beautiful. People will see the Paper Phone on May 10 this year.