Physiology means the scientific study of function in living systems. It mostly focuses on how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The different divisions are human physiology, animal physiology, plant physiology, cellular physiology, microbial physiology, bacterial physiology, viral physiology. High-impact journals are those considered to be highly influential in their respective fields. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information. The impact factor of a journal is evaluated by dividing the number of current year citations to the source items published in that journal during the previous two years.