At the time when he discovered what we now call gamma rays, Villard was working in the chemistry department of the École Normale Supérieure rue d'Ulm, Paris.

He spent the early part of his career (1888–1896) focusing on similar compounds at high pressure.

Villard investigated the radiation emitted by radium salts via a narrow aperture in a shielded container onto a photographic plate, through a thin layer of lead that was known to stop alpha rays.

Villard was a modest man and he did not suggest a specific name for the type of radiation he had discovered.

Villard spent much time perfecting safer and more accurate methods of radiation dosimetry, which had been done very crudely up until then (typically by evaluating the quality of the image of the experimenter's hand produced on a photographic plate).