Normal science is a concept originated by Thomas Samuel Kuhn and elaborated in The Structure of Scientific Revolutions. The term refers to the regular work of scientists experimenting within a settled paradigm or explanatory framework. Regarding science as puzzle-solving,  Kuhn explained normal science as slowly accumulating detail in accord with established broad theory, without questioning or challenging the underlying assumptions of that theory.
The route to normal science
Kuhn stressed that historically the route to normal science could be an arduous one. Prior to the formation of a shared paradigm or research consensus, would-be scientists were reduced to the accumulation of random fact and unverified observations, in the manner recorded by Pliny the Elder or Francis Bacon, while simultaneously beginning the foundations of their field from scratch through a plethora of competing theories.
Normal science at work
Kuhn considered that the bulk of scientific work was that done by the 'normal' scientist, as he or she engaged with the threefold tasks of articulating the paradigm, precisely evaluating key paradigmatic facts, and testing those new points at which the theoretical paradigm is open to empirical appraisal.
The breakdown of consensus
For the normal scientist anomalies represent challenges to be puzzled out and solved within the paradigm. Only if an anomaly or series of anomalies resist successful deciphering long enough and for enough members of the scientific community will the paradigm itself gradually come under challenge.
In this way however, according to Kuhn, Normal science possesses a built-in mechanism that ensures the relaxation of the restrictions that previously bound research, whenever the paradigm from which they derive ceases to function effectively. 
Karl Popper has criticised Kuhn's view of normal science as excessively conservative and dogmatic—though whether Kuhn is prescriptive or merely descriptive here is open to doubt. Popper (and others) have also questioned whether the contrast between normal science versus revolutionary science is as stark as portrayed by Kuhn.
- J. Childers/G. Hentzi eds., The Columbia Dictionary of Modern Literary and Cultural Criticism (1995) p. 110
- Childers, p. 84
- T. S. Kuhn, The Structure of Scientific Revolutions (1970) p. 35-42
- Kuhn, p. 10-22
- A. Rosenberg, Philosophy of Science (2005) p. 149
- Kuhn, p. 25-8
- Kuhn, p. 52-78
- Kuhn, p. 181
- R. J. Bernstein, Beyond Objectivism and Relativism (2011) p. 69-70
- Bernstein, p. 70
W. O. Hagstrom, The Scientific Community (1965)