Frans Janssens was born in
Sint-Niklaas, the son of
Theodoor Janssens, a politician. He was ordained as a priest on 18 September 1886, and obtained a PhD in Natural Science in 1890, with the highest honors and a scholarship to attend many prestigious foreign laboratories. In 1891 he became a teacher in Ghent. He was sent by his bishop to the brewery school in Munich, then to the
Carlsberg Laboratory in Copenhagen, where he worked with
Johan Kjeldahl and
Emil Christian Hansen. He returned to Belgium, where he co-founded a brewery school and taught bacteriology. In 1896, he joined the Faculty of Sciences for the
Catholic University of Leuven, as a professor in
microscopy, and from 1899 in
cytology, succeeding
Jean-Baptiste Carnoy in the chair. Janssens was also president of the
Societé Belge de Biologie and a
Canon (priest) at the
Sint-Baafskathedraal in
Ghent. He died in
Wichelen. ==Research==