Microfilming, also called microphotography, consists in the reduction of images to such a small size that they cannot be read without optical assistance. This amazing photographic compression often results in a ninety-nine percent saving of space. The microfilming service is one of the most extensively used and common practices in modern reprographic science. With the advancement in the field of documentary reproduction, the function of the library is not only restricted to classification, and handling of printed materials but to documentation, in the form of microfilm, which is becoming a major factor in library science, particularly where reproduction is essential for preservation purposes. The remarkable increase in microfilming activities is due to the recognition that a large portion of books, periodicals and newspapers are deteriorating because of the poor quality of paper and print. The use of microfilming for almost seventy years has provided an excellent reproduction method for recording photographic images of library materials.

Preservation of rare and deteriorating documents is considered one of the most important purposes in micro-recording. Valuable rare documents are now being microfilmed to preserve them from loss and destruction. Although the principles of microfilming have been known for over 150 years, it is only after the Second World War that the use of microfilming methods became very popular as a technique for reproducing the printed page. In the case of valuable documents, which might become damaged by constant use, a microfilm copy of it may be made and stored separately. It must be protected against loss, which would be irrecoverable in the case of valuable documents, records or rare books. The film used is safety film and if properly processed it will last longer than the originals. If possible, the microfilm copy may be given to the reader for reference purposes which not only prevents the original from damage by constant use but will also protect it from danger, such as fire, natural disaster, etc. For additional security, negatives and positives can be stored in different places; being of small bulk, it can be specially protected. Scientific estimate indicates that a negative with careful handling and storage could be preserved for about 500 years.

Advanced leaders in American government and photographers have long been aware of the need for microfilming.

"Time and accident are committing daily havoc on the originals (of valuable historic and state papers) deposited in our public offices. The late war has undone the work of centuries in this business. The lost cannot be recovered; but let us save what remains; not by vaults and locks which fence them in from the public eye and use in consigning them to the waste of time, but by such multiplication of copies as shall place them beyond the reach of accident."
--Thomas Jefferson, February 18, 1791

"... because of the conditions of modern war against which none of us can guess the future, it is my hope that it is possible to build up an American public opinion in favor of what might be called the only form of insurance that will stand the test of time. "I am referring to duplication of records by modern processes like microfilm so that if in any part of the country original archives are destroyed a record of them will exist in some other place."
--Franklin D. Roosevelt, February 13, 1942

"The microscopic uses of the photograph have merely been hinted at, never tried more than interesting experiments. Let us imagine the number of wills or mortgages liable to be destroyed, which would cause boundless litigation …A microscopic negative of which, carefully stored away… would give a document as reliable as the original. Hundreds of thousands of such negatives might be put away to be resuscitated upon the loss of the objects from which they were taken… I trust that it will be the custom to make microscopic negatives of all valuable public documents."
--American Journal of Photography, 1858

"The whole archives of a nation might be packed away in a small snuff box. Had the art been known in the time of Omar, the destruction of the Alexandrian Library would not have been a total loss."
--Photographic News, 1859