Biology is the study of living beings, all plants and animals, including humans. Biology had significantly flourished in ancient India during 2500 B.C. to 650 B.C. The roots of biology can be traced back to pre-historic periods when primitive man lived in jungles and caves. Biology has slowly grown through the ages, but developed very fast in the 20th century and is showing signs of even faster growth in the 21st century. Knowledge of biology has greatly helped us in the field of human health. It helps us to understand the cause of many diseases. We can identify various micro-organisms that cause diseases in man. We can study their mode of living and the different ways in which they spread diseases. The understanding of disease-causing micro-organisms has led to the development of new drugs, both natural and synthetic drugs that can kill these organisms. Modern biology is a vast and eclectic field composed of many specialized disciplines that study the structure, function, growth, distribution, evolution, or other features of living organisms.