In 1931, François Kollar began his collaboration with Horizons de France publishing house, for a series of reports on French people at work, in a book to be published under the title "la France Travaille". This investigation, rich of more than 2.000 pictures and which will last nearly 4 years, takes François Kollar all over the country, where he photographs all the sectors of industry and agriculture. "La France Travaille" was published in the form of fascicles starting in 1932 and with great public and critical success.