Unknown K.M. Derjugin
The biographical article dedicated to life story and scientiﬁc activity of well-known Russian hydrobiologist and zoologist K.M. Derjugin. It is made according to published and unpublished (archive) materials as well as based on interviews with people who new the scientist. Life story of the scientist is considering from the "living biography" position, where personality of the man is more important instead of enumeration and review of his studies. The biographical article is heralding publication of the daily notes made by Derjugin in 1899 placed in the issue. Many of photos provided in the publication had not been well-known before.