Fourth volume in *Les Gagne-misère*, *La Boîte à lumière* gathers recollections and observations around work, trades, and the social worlds built around them. Its focus is on occupations that shaped everyday life, especially small trades and artisanal practices often preserved through memory rather than official history. The book treats these livelihoods as cultural evidence: how people learned a craft, adapted to hardship, negotiated status, and passed knowledge from one generation to the next. Through personal narrative and historical attention, it offers a portrait of working communities and the customs that surrounded them, emphasizing the dignity and complexity of modest or disappearing trades.