Every living cell, every living organism is a complex chemical laboratory, whose perfection has already been admired by more than one chemist. Thousands of chemical reactions take place in the cell every minute, involving the complex synthesis of important substances at the expense of the breakdown of other, simpler compounds. A living organism is inextricably linked to its environment. It constantly exchanges chemical substances with it. Mineral salts and nutrients are absorbed, and the products of its vital activity are excreted. Since our environment consists of inanimate matter and living organisms, every inhabitant of our planet is directly or indirectly connected with both the inanimate and the living world. These complex relationships were first recognized by the great French chemist Antoine Lavoisier (1743–1794; discoverer of oxygen and silicon). In his historic work “The Circulation of Elements on the Earth's Surface,” he writes: “Plants obtain the substances necessary for their life from the surrounding air, water, and the entire inanimate world. Animals feed either on plants or on animals that feed on plants, so that the substances of which their organism is composed ultimately originate from the air and the mineral kingdom. Finally, through fermentation, decay, and combustion, all these substances taken from plants and animals are constantly returned to the air and the mineral kingdom.”