A scientist, in a broad sense, is one engaging in a systematic activity to acquire knowledge. In a more restricted sense, a scientist is an individual who uses the scientific method. The person may be an expert in one or more areas of science. This article focuses on the more restricted use of the word. Scientists perform research toward a more comprehensive understanding of nature, including physical, mathematical and social realms. Philosophy can be seen as a distinct activity, which is aimed towards a more comprehensive understanding of intangible aspects of reality and experience that cannot be physically measured. Scientists are also distinct from engineers, those who develop devices that serve practical purposes. When science is done with a goal toward practical utility, it is called applied science (short of the creation of new devices that fall into the realm of engineering). When science is done with an inclusion of intangible aspects of reality it is called natural philosophy. Technologists are employed in a large and wide-array of industries, including manufacturing, construction, industrial, maintenance, and management. They may be hired as managers of technology, depending on the technologist's educational emphasis on management preparation. This biographical encyclopaedia provides readers with of some of the basic knowledge of World Great Scientists and Technologists.