“We deal with art thinking we can start from thoughts,” the Italian artist Maria Lai said near the end of her long life. “Instead, first of all we need to fall in love with a material.” This she did. From thread and fabric, the stitch and the loom, Lai made art that looks stolen from a fable, or from a library of work written in a lost language. On the centennial of her birth, MAXXI pays tribute to Lai’s charming, haunting creations. —J.V.