|Are totipotent cells which are basically undifferentiated biological cells having the capability to differentiate into various organs by the process of mitosis. They are found commonly in multicellular organisms. In case of mammals, there are two divided into: embryonic stem cells, which are obtained from the inner cell mass of blastocysts, and adult stem cells, which are found in various tissues. In matured organisms, stem cells and progenitor cells act as a repair system for the body, replenishing adult tissues. 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.