A scientist, in the broadest sense, refers to any person that engages in a systematic activity to acquire knowledge or an individual that engages in such practices and traditions that are linked to schools of thought or philosophy. In a more restricted sense, scientist refers to individuals who use the scientific method. The person may be an expert in one or more areas of science. There are notable examples of people who have moved back and forth among disciplines. Such polymaths were common during the Islamic Golden Age and European Renaissance. Those considering science as a career often look to the frontiers. These include cosmology and biology, especially molecular biology and the human genome project. Other areas of active research include the exploration of matter at the scale of elementary particles as described by high-energy physics, and nanotechnology, which hopes to develop electronics including microscopic computers, and perhaps artificial intelligence. The books (in five volumes) contain the life and work of World Great Scientists.