In 1984, GRATALOUP participated in a competition organized by the Assistance Publique de Paris. A number of artists, known at the time, were pre-selected for the interior decoration of the entrance hall of the new Saint-Louis Hospital, whose construction has just been completed. At the end of the competition, GRATALOUP is selected for the realization of a stained glass window of 25 m2. The artist will opt for a theme that is dear to him, that of the Tree of Life, subject in perfect relation to the universe of health and hospital.

The stained glass window will be realized in collaboration with the master glassmaker Meliava. It was inaugurated by the Prime Minister, Pierre Bérégovoy, accompanied by Jack Lang, then Minister of Culture.

"As I had already done, I had to find a master glassmaker to work together, preferably in Paris. Not found! Gone or retired. It was by chance, rue de la Contrescarpe, that I came across a plaque in the name of Meliava, master glassmaker. It will be him. The model was enlarged into several parts in his small workshop. We were happy because we were going to show «the Tree of Life». The stained glass window started from a dark (blue) structure towards a brighter (yellow). The glasses were selected and cut, and then placed in their metal locksmith. The Saint-Louis Hospital was a little below street level. The stained glass window was put in place. But O surprise! The blues, which looked very bright in the workshop, were completely extinguished in the new situation. We brought huge spots to light up public buildings, but nothing happened. We then brought a mirror that slightly revived the blues but insufficiently. What to do? Only one solution; start the base of the stained glass. And finally, we had to redo the whole base. It was a big job, but our reputations were at stake…. In fact, sunlight is absolutely incomparable!”.