Trans activists at the International Congress for Sex Reform on the Basis of Sexology, Berlin, 1921.
The library of the Institute for Sexual Science was raided by the Nazis in 1933, and many rare books on sex and gender were burned.
The private library of Dr Magnus Hirschfeld (he appears to be pictured standing behind the trans activists in the first photo), the founder of the institute, was also raided and his books burned.