In the world's first media interview, shot in Paris in August 1886, the great photographer Nadar interviews the famous scientist and sceptic Chevreul on his 100th birthday. In their own words - originally recorded in shorthand - they discuss photography, colour theory, Moliere, the scientific method, the crazy ideas of balloonists, and - of course - how to live for 100 years. These two legends of the 19th century have a lively and interesting conversation. One was born before the French revolution; the other was destined to see the marvels of the aeroplane and the movies.