Dreams may be more important than sleep. Some people don't need much sleep. But we all need to dream, scientists say.

    Dreams take up about one quarter of our sleeping time. People have several dreams each night. Dreams are like short films. They are usually in color. Some dreams are like old films. They come to us over and over again. That may be because the dreamer is worrying about something. Dreaming may be a way of trying to find an answer.

    Some people get new ideas about their work from dreams. They could have been thinking about their work all day. These thoughts can carry over into dream. Sometimes we wake up with a good feeling from a dream. But often we can't remember the dream.

    Dreams can disappear quickly from memory. Too much dreaming can be harmful. The more we sleep, the longer we dream. The mind is hard at working when we dream. That is why we may have a long sleep and still wake up tired.

    It is important for us to look after the Earth well. The Earth gives us a lot of things. We also give the Earth a lot, but some of the things are not good.

    In nature, when something dies, other animals and plants get food from it. Every animal or plant provides food for other animals or plants. However, animals can't get food from many of the things that we"give" the Earth. Animals and plants can't cat metal, plastic or glass. These things will stay in the ground for many, many, many years.

    Some rubbish is very dangerous for plants and animals. In some places, many animals live together. One animal makes food for many other animals. If we throw rubbish and chemicals into the water, the plankton（浮游生物）can die. If there isn't any plankton, many animals have nothing to eat.

    So what can we do? Don't leave any rubbish in the countryside! Don't make so much rubbish.

    Man has a big brain（大脑）. He can think, learn and speak. Scientist once thought that men are different from animals because they could think and learn. They know now that dogs, rats, birds can learn too. They are beginning to understand that men are different from animals because they can speak.

    Animals cannot speak. They make noises when they are afraid, or angry or happy. Apes（类人猿）can understand some things more quickly than men. One or two of them have learnt a few words. But they cannot put words together to make sentences. They cannot think as we do because they have no languages. The language is a wonderful thing. Man is able to build a modern world because he has language.

    Each child can speak his own language very well when he is four or five, but no animal learns to speak. How do children learn it? Scientists don't know. They only know that man can speak because he has the brain.

    Have you ever dreamed about a trip to the space? Seeds (种子) of some vegetables and crops are a lot luckier than you, as they have travelled to space and back.

    China is among the three countries in the world that carry out agricultural research (农业研究) in space. The others are Russia and the US.

    Since 1987, China has sent about 1, 000 species of seeds into space.

    These include green peppers, tomatoes, cucumbers (黄瓜), carrots, lettuce and wheat. Even on China's first manned spacecraft Shenzhou—V, there were some seeds from Taiwan.

    "Conditions in outer space such as radiation (辐射) and low gravity can cause big changes in the seeds," said Chinese researcher Jin Xing.

    But not all seeds are better after going to space. After returning to the Earth, the best seeds are selected. These seeds produce (生产) much more and also grow faster than normal (正常的) seeds

    We all know that many inventions have changed our life a lot. They play important roles in our daily life. Here are some interesting inventions.