In science, priority is the claim and recognition of first discovery or theory. Fame and honors usually go to the first person or group to publish a new finding, even if several researchers arrived at the same conclusion independently and at the same time.

Priority becomes a difficult issue usually in the context of priority disputes, where the priority for a given theory, understanding, or discovery comes into question. In most cases historians of science disdain retrospective priority disputes as enterprises which generally lack understanding about the nature of scientific change and usually involve gross misreadings of the past to support the idea of a long-lost priority claim. Historian and biologist Stephen Jay Gould once remarked that "debates about the priority of ideas are usually among the most misdirected in the history of science."

In the cases of scientists who have since achieved incredible levels of popularity, such as Charles Darwin and Albert Einstein, priority questions are often rooted in taking too seriously the myth of the "lone genius" which is often cultivated around such quasi-mythic figures (see Great Man theory and Whig history). In an attempt to laud such scientists as visionaries, the context in which they worked is often neglected by popularizers, making it appear as if they worked without assistance or without reference to other work, something which is rarely the case.

Craig Cameron Mello (born October 18, 1960) is an American biologist and professor of molecular medicine at the University of Massachusetts Medical School in Worcester, Massachusetts. He was awarded the 2006 Nobel Prize for Physiology or Medicine, along with Andrew Z. Fire, for the discovery of RNA interference. This research was conducted at the University of Massachusetts Medical School and published in 1998. Mello has been a Howard Hughes Medical Institute investigator since 2000.

Mello was born in New Haven, Connecticut on October 18, 1960. He was the third child of James and Sally Mello. His father, James Mello, was a paleontologist and his mother, Sally Mello, was an artist. His paternal grandparents immigrated to the US from the Portuguese islands of Azores. His parents met while attending Brown University and were the first children in their respective families to attend college. His grandparents on both sides withdrew from school as teenagers to work for their families. James Mello completed his Ph.D. in paleontology from Yale University in 1962. The Mello family moved to Falls Church in northern Virginia so that James could take a position with the United States Geological Survey (USGS) in Washington, DC.