Merceries are stores that typically have all sorts of lovely notions related to sewing and sometimes some yarn as well. One of my favorite merceries in Paris is Entrée des Fournisseurs, 8 rue des Francs Bourgeois, 75003. It is a magical shop located in a somewhat hidden courtyard in the heart of the Marais.
I was only able to sneak a few photos because the store does not allow photographs to be taken. Unfortunately, my photos do not do justice to the quaintness of this shop, so I really hope you can stop by sometime and see it for yourself.