From Wallpaper.com:

Hair artist Julien D’ys is one person never low on artistic output. Over the years, he has amassed hundreds of notebooks all bursting with sketches, paintings and photographs that have formed the basis of his work with Comme des Garçons, John Galliano, Karl Lagerfeld and Marni, to name a few. ‘My notebook is like my brain,’ D’ys says. ‘I draw, I think, from there I built my idea and bring it in life.’

See more: Peek inside the notebooks of Comme des Garçons’ hair artist