Our universe's smallest galaxies hold the largest star factories. Here's why 

 Conditions within dwarf galaxies initially produce more stellar-mass black holes than supernova explosions.  

https://cdn.mos.cms.futurecdn.net/94NqdiCBxUa7NQgAT9TnyX.jpg

https://www.space.com/small-galaxies-star-forming-nebulas-black-hole-metallicity