It was 2055 when the world was hit by a massive catastrophe due to which the overall temperature of the earth started dropping down. When the temperature dropped below the tolerance level (around year 2070) humans were forced to reside inside caves
It is the year 2087 now, and the temperature is -230°C. Humans have locked themselves in cryogenic chambers in order to preserve their body, and transfer their consciousness to humanoid robots, in hope that one day everything will be back to normal