In 1863 Poland was occupied by the Russian Empire. The same year, the public use of the language was banned, and at the same time a great effort was made by the Russians to destroy the Polish culture as well.
It was then that Polish organized a secret education system, which was initially launched in homes. Later, these scattered schools merged at a secret university called “Flying University” “Uniwersytet Latający”, which operated until 1905 in Warsaw. It is worth noting that Marie Curie was a student at the Flying University.