Chrys Millien studied computer sciences, a specialty that comes in handy in his science fiction comics. He made his debut with the social sci-fi series 'Witness 4', which he drew in a style influenced by both manga and the Clear Line. The scripts were written by Erik Arnoux and three books were published by Soleil Productions between 2001 and 2005. He has continued to work with Arnoux on several later projects. Millien was the colorist and co-artist of the crime comic 'Poker Face', which was drawn by Arnoux and written by Jean-Louis Fonteneau for (Jungle! in 2011-2012. The trio also cooperated on the historical comic 'Les Génies de l'Arc de Triomphe' (Glénat, 2013). Millien and Arnoux draw the historical aviation comic 'L'Aviateur' from scripts by Jean-Charles Kraehn for Dargaud since 2016.
On his own, Millien wrote and drew an adaptation of Jules Verne's 'Around the World in 80 Days' for the collection 'Romans de toujours' of Éditions Adonis in 2007. The book was reprinted by Glénat in 2010 and 2016. He then worked with Richard D. Nolane on 'Dumarest L'Aventurier des Étoiles', an adaptation of the space novel series 'Dumarest of Terra' by the British writer E.C. Tubb. The project was cancelled after one book (Soleil, 2009), however.