Volumes 18, 19, and 20 of Alle de Brieven / Collected Letters became available at the end of 2024, completing the series begun in 1939. Download for free.

Master list (pdf) of all 602 L-numbers, their Leeuwenhoek number, and their Collected Letters number

Letter 18 (AB 26) of October 9, 1676, is Leeuwenhoek's most famous letter, the one in which he describes in detail the microbes in his infusions. Note the links there under Publication history and Learn more to all of the pages, events, and sources related to this letter on Lens on Leeuwenhoek.