The Preprints collection aims to cover as far as possible all the grey literature in particle physics and its related technologies. The collection contains something like 400,000 documents, out of which about 50% can be accessed electronically. The documents originate from a variety of institutes all over the world. The collection, currently available, starts in 1979 and it has a full coverage of the arXiv.org e-Print archive since its beginning in 1991.