In the field of sociology, his ideas where original and new. While almost all great sociological theorists thought of the physical/material world as an environment that coexists with the social world of humans or as background noise with negligible influence, Latour came up with a theoretical framework that allowes us to incorporate the physical world, flora and fauna into the social construction of reality.

Edit: To make it a little bit clearer. Latour thought of all kind of things, like stones, keys, bacteria, doors and so on, as social actors that had to be taken into the equation. For him, they where as important as humans when it came to action and the questions why we act and why we act in a certain way.