Sustainable development? At the Rio Conference in 1992, the UN decided that everyone must work on sustainable development, which the UN defines as follows: "development that meets the needs of the present without compromising the ability of future generations to meet their needs" However, through the laws of the nature, the Earth sets uncompromising conditions. We are all aware of the law of gravity, which keeps us on the ground. Another law, which is not so obvious, is that "Nothing disappears, everything spreads". This means that no material and no energy can disappear, but can only be converted and spread. This is going on around us constantly, but unlike the law of gravity, which works instantaneously, the spread takes place after a time lag, which makes it less apparent to us. In order that our future generations shall not lack resources and be exposed to environmental problems, we must observe the Earth's game rules: 1. Avoid substances from the Earth's crust. Oil and most metals cause us problems if left in the environment . 2. Avoid substances that nature can not handle. Many man-made substances can not be handled by nature, which gives us problems in the form of dangerous toxins. 3. Take care of the nature. We must safeguard animals and nature and must not take more from nature than it can afford to give us.