The fragile boundary between death and life has been a subject of art since the earliest recorded cultures. In Classical sculpture, scenes of death ranged from highly dramatic mythological scenes to the deeply introspective last moments of mortal subjects. On a more intimate scale, the pietà (Mary mourning of the body of Christ) became a commonly painted and sculpted subject beginning in the 13th century in Northern Europe; it soon spread to the south, and continued to appear regularly into the 17th century. The vanitas image, a reflection on the transitory nature of human existence that includes memento mori like skulls or hourglasses, was popularized in 17th-century Netherlands. From the 18th to the 19th centuries, French painting saw a shift from the admiring scenes of mortal struggle by Romantics to sedate scenes by Realists, such as Gustave Courbet’s Burial at Ornans. In 20th century Western art, reflections on mortality range from scenes of brutal atrocity (e.g. Pablo Picasso’s Guernica) to the self-destructing machines of Jean Tinguely, to homages to the victims of AIDS (by Nan Goldin and Felix Gonzalez-Torres, amongst others).