Complex sentence: The Renzo Piano-designed museum opened to the public in June 1987 and houses the de Ménils' privately-assembled collection of twentieth-century art, including some 15,000 paintings, sculptures, prints, drawings, photographs, and rare books.
Split into simpler sentences: The Renzo Piano-designed museum opened to the public in June 1987 and houses the de Ménil's privately-assembled collection of the twentieth century. It is made up of approximately 15,000 paintings, sculptures, prints, drawings, photographs, and rare books.