Fyi OP is wrong its not actual Human remnants, its a art project to show the horror of nuclear war
According to museum staff, many visitors to the museum believe that the shadow is the outline of a human vaporized immediately after the bombing.[4] However, the possibility of human vaporization is not supported from a medical perspective. The ground surface temperature is thought to have ranged from 3,000 to 4,000 degrees Celsius just after the bombing. Exposing a body to this level of radiant heat would leave bones and carbonized organs behind. While radiation could severely inflame and ulcerate the skin, complete vaporization of the body is impossible.