How come some people have their hearts on their left side?

Question: How come some people have their hearts on their left side?
- Keywords:
  heart,
  left
Asked by KMB to Huma, Jack, Lucy, Miranda, Peter on 16 Nov 2016.
- Lucy Oldacre-Bartley answered on 16 Nov 2016:
  
  All of us have most of our heart on the left side – although there is a little bit on the right.

Question: How come some people have their hearts on their left side?