"Spheres" deals with "spaces of coexistence", spaces commonly overlooked or taken for granted which conceal information crucial to developing an understanding of humanity. The exploration of these spheres begins with the basic difference between mammals and other animals: the biological and utopian comfort of the mother's womb, which humans try to recreate through science, ideology, and religion. From these microspheres (ontological relations such as fetus-placenta) to macrospheres ("macro-uteri" such as states), Sloterdijk analyzes spheres where humans try but fail to dwell and traces a connection between vital crises (e.g., emptiness and narcissistic detachment) and crises created when a sphere shatters.