L'Oréal Professionnel is celebrating its 100th anniversary this year -- and kicked off a three-day celebration with an opening party at the Carrousel Du Louvre in Paris. 

The evening was hosted by Nathalie Roos, president of L'Oréal's Professional Products Division and Marion Brunet, International general manager, L'Oréal Professionnel. 

Alexa Chung, the brand's spokesperson, greeted guests. Attendees included 1,700 hair artists from 40 countries -- and celebrity friends, including: Catherine Deneuve, Virginie Ledoyen, Elsa Zylberstein, Ellen Von Unwerth, Stefi Celma, Alexandra Golovanoff, Camille Charrière, Alexis Mabille, Franck Provost.

The festivities included a hair show, "La French, Art of Hair Coloring," along with live musical showcases.

Guests were invited to discover 110 years of innovation through all L'Oréal Professionnel iconic products -- and to learn about the brand's latest product innovation, Majirel Glow. 

The team also demonstrated the tech innovation, L'Oréal Professional's new app -- Style My Hair Pro. The app is designed to transform the in-salon hair color consultation experience. The app features a 3D try-on technology and an exclusive digital swatch book. It is already used by more than 20,000 hairdressers in salons.

The opening night party was followed by a three-day event, including a series of workshops and masterclasses led by a range of prestigious hosts, speakers and mentors. The sessions explored the brand's signature theme, "La French Art of Hair coloring."

L'Oréal Professionnel also hosted an international grand final and winners' celebration of the Style & Colour Trophy at the Salle Pleyel in Paris.