Assertion: semen's sperm | /r/HasProperty | observed under microscope
Facets:
value: by antonie van leeuwenhoek
type: OTHER
value: in 1677
type: TEMPORAL
Source sentences:
text: Sperm were first observed under a microscope in 1677 by Antonie van Leeuwenhoek who described them as little animals or animalcules.