Man of Steel, Woman of Kleenex is a 1969 essay in which science fiction author Larry Niven details the problems that Superman would face in sexual intercourse and reproduction with a human woman, using arguments based on humorous reconciliation between physics, biology, and the abilities of Kryptonians as presented in Superman comic books. The issues discussed include Superman's loss of physical control during intercourse, the presumed "super powers" of Superman's sperm cells, genetic incompatibility between humans and Kryptonians, and the dangers to the woman during gestation. The title is a reference to Superman's power and invulnerability, contrasting it with the relative fragility – like Kleenex brand facial tissue – of a human. The hypothetical woman is referred to in the essay as "LL