If you look at a house from far away, you might see some of its features, such as doors and windows. If you go nearer to the house, you might find that it is made of bricks. When you look closely, you can see that the house is made of many bricks.

The bricks are the building blocks (块) of the house.

Your body has building blocks too. They’re called cells. The bodies of plants and animals are very different from one another, but they all have one thing in common—all are made up of cells. There are many different kinds of cells in your body. Each kind of cell has its own job, such as muscle (肌肉) cells, bone cells, and blood cells.

Cells work together to keep your body alive. A group of similar cells that work together to do the same job form a tissue (组织). The human body is   made of different kinds of tissues. Muscle tissue and nerve (神经) tissue are two kinds of tissues.

An organ is a group of different kinds of tissues that work together to carry out a certain job. Each kind of organ in your body has a special job to do. Some examples of organs are your stomach, heart and skin.

Like cells and tissues, organs work in groups too. A group of organs that work together to do a certain job is called an organ system (系统). All the organ systems in your body work together to keep you alive. These systems can be put into the two groups—Support and Control Systems as well as Energy and Transport Systems.

Leaves are falling. The wind gets cold. November 7 is lidong. It is the beginning of winter. Lidong is one of the 24 solar terms (节气). Chinese people usually have a big meal on that day. Eating well can help people keep warm on cold days. In the north, people usually eat dumplings. In the south, people eat chicken, duck and fish. In the old days, lidong was also a time for people to store (存储) vegetables. At that time, there were not many fresh vegetables to eat during winter, especially (尤其) in the north. There were also no supermarkets like today. People had no place to buy fresh vegetables in winter. So, around lidong people put lots of cabbages in a cellar (地窖). They also made fresh tomatoes into tomato sauce (酱). It was good for eating noodles in winter.

“Early to bed and early to rise makes a man healthy, wealthy and wise.”

This is an old English saying. It means that we should go to bed early at night and get up early in the morning. If we do, we shall be healthy, rich and clever.

Is this true? Perhaps it is. The body must have enough sleep. Children at the age of six to thirteen need at least nine hours’ sleep every night. If you go to bed late, you can’t have enough sleep. Then you can’t think carefully and your homework will be wrong. You will not be wise and you may not become wealthy!

Some people go to bed late at night and get up late in the morning. This is not good for them. We should sleep at night when it is dark. The dark helps us sleep well. When the daylight comes, we should get up. This is the time for exercise. If the body is not used, it will become weak. Exercise can keep it strong. So we should do some exercises regularly.

Exercise helps the blood (血液) to move around inside the body. Blood takes nutrition (营养) to all parts of our bodies. The brains (大脑) in our heads also need blood. We think with our brains. If we keep our bodies healthy, and take exercise often, we can think better!

Our bodies also need fresh air. Without air we will die. Get up early in the morning and we can have plenty of clean, fresh air. That will keep us healthy and happy.