Agricultural science is not a single discipline, save that the men and women who are involved have a common purpose in improving the provision of food from resources of land and climate. It draws heavily on the basic physical and biological sciences and, indeed, contributes to them. Much of agricultural science is engendered by realisation of real problems in agriculture, some by an appreciation of likely future ones and some by curiosity and wonder about the nature of the living things on which we all depend. Each year literally millions of scientific papers are published which advance the front of our knowledge about the many factors which contribute to the productivity of soils, plants and animals. To summarise such a wealth of information and give recognition to the many who have made contributions to our understanding would be a Herculean, if not an impossible, task. In the chapters which follow there has, of necessity, been selection in which an attempt has been made to give prominence to those discoveries and inventions that have had the greatest impact. Furthermore, science is a vast continuum and some of the signal scientific advances were made long before they were applied to what was in the 1930s a craft industry to transform farming into the science-based agricultural industry of the present. These early discoveries are mentioned where appropriate.