There are extreme environments on Earth where life seems impossible. In these environments, micro-organisms rule and animals display strange adaptations. Scientists are studying how these species manage to survive with so little oxygen, food and light in the most inhospitable caves of our planet.
The Movile Cave in Romania is the most extreme subterranean environment on Earth. Its isolation for several millions years has led to the creation of a special microcosm where the concentration of hydrogen sulphate is 100 times that of the air we breathe. And yet, a rich ecosystem has developed in this hell, thanks to the action of certain microbes.On the other side of the world, in another tiny underground microbial paradise in Mexico, there flows a stream that is almost an opaque white, and yet a curious species of fish lives in it. This fish has developed strategies for living in water saturated with hydrogen sulphate.In Slovenia a mysterious creature, the proteus, has human-like skin, pink and transparent, and manages to survive without food for many months.
The need to adapt to extreme environmental conditions has required living creatures to change in many different ways which include loss of skin color, blindness, resistance to an acid atmosphere.
The amazing sequences of this film unveil these unusual environments as well as the uninterrupted interactions of living beings struggling to achieve a fragile, often completely unexpected balance.