Who is regarded as one of the most important astronomers of all time, and invented a morphological classification scheme for galaxies?
Hubble sequence: The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in 1926. Edwin Hubble:  He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology and is regarded as one of the most important astronomers of all time.
Edwin Hubble