Highlight from 'Astrophysics for People in a Hurry' by Neil deGrasse Tyson

the tally of local dwarf galaxies has been counted in the dozens. While full-blooded galaxies contain hundreds of billions of stars, dwarf galaxies can have as few as a million, which renders them a hundred thousand times harder to detect. No wonder they are still being discovered in front of our noses.
— Neil deGrasse Tyson, Astrophysics for People in a Hurry