Passionate by rock climbing and intensive fieldwork, from 2012 to 2016 Guillaume studied elite professional climbers in the USA and Europe, with the aim to describe and analyze their everyday work and life, leading to the publication of his first book (Professional climber, Ehess, 2018).

From 2017 to 2019, funded by a Juan de le Cierva Grant from the Spanish Ministry of Economy, Guillaume spent 18 months at a business accelerator for social impact start-ups. By conducting organizational ethnographic fieldwork, he studied how social entrepreneurs, impact investors, and corporations collaborate to create social and economic value.

From 2019 to 2021, Guillaume has been involved in two research projects funded by the Spanish Ministry of Economy and the Fundación Reina Sofia to study digital inequalities and the use of ICTs for online job search. With an interdisciplinary and international team, he has been conducting more than 80 semi-structured interviews with job seekers and recruiters.

In 2021, he started “VeUs – Raval”, a five-years project on the Barcelona’s narcotics market. Based on ethnographic fieldwork in the emblematic neighborhood of “El Raval”, the project helps explaining this phenomenon by studying multiple processes and actors, among which the growth of the “narcopisos”, social movements, supervised drug consumption rooms and harm reduction policies, initiatives to help drug users (e.g., peer-driven drug user, safe supply), and gentrification and police pressures.