What forms black hole? Why are black holes made? And What are they made out of?

Question: What forms black hole? Why are black holes made? And What are they made out of?
- Keywords:
- Royal Society of Chemistry: Find out more on:
  
  black hole
  
  space
  
  universe
Asked by to Kate, Kieren, Rowena, Roy on 19 Mar 2014. This question was also asked by .
- Rowena Fletcher-Wood answered on 19 Mar 2014:
  
  Black holes are the densest thing, where matter gets so mashed together it is no longer recognisable as matter. Because they are so dense they have a huge gravitational pull and drag everything in from around them. One way black holes can be made by stars dying and contracting in once they have used up all their fuel – they are made of all the matter that is left over.

Question: What forms black hole? Why are black holes made? And What are they made out of?