In ancient times before the development of natural science, people were puzzled by colorful creatures. They often regard life and inanimate objects as two completely different and unrelated fields, and think that life is not dominated by the laws of motion of inanimate objects. Many people also attribute all kinds of life phenomena to an immaterial force, that is, the role of "vitality". These groundless speculations have been gradually abandoned with the development of biology and have no place in modern biology. Since the 20th century, especially since the 1940s, biology has absorbed the achievements of mathematics, physics and chemistry, and gradually developed into an accurate, quantitative and molecular science. People have realized that life is a form of material movement. The basic unit of life is the cell, which is a material system composed of protein, nucleic acid, lipid and other biological macromolecules. Life phenomenon is the expression of the comprehensive movement and transmission of matter, energy and information in this complex system. Life has many characteristics that inanimate matter does not have. For example, life can synthesize a variety of organic compounds at normal temperature and pressure, including complex biological macromolecules; It can make use of substances in the environment, so that all kinds of substances in the body far exceed the production efficiency of the machine, without discharging harmful substances that pollute the environment; Can efficiently store and transmit information; It has self-regulation function and self-replication ability; It is of great theoretical and practical significance to carry out individual development and species evolution in an irreversible way and reveal the mechanism in the process of life.
Modern biology is a huge knowledge system with many branches. This paper focuses on the objects, branches, methods and significance of biological research. The essence of life and the history of biological development will be expounded in "life" and "biological history" respectively.