Typical data science is done on structured data such as tables, sometimes on unstructured data such as text, but graph is a bit different than both, unstructured as well as variable size. This talk gives overview of the challenges and how to apply Data Science on Graphs. It will start with introduction to graphs, then its challenges then will enumerate graph algorithms. At the end it will take up a few applications and then conclude with the next steps. The talk will also mention the practical usage using Neo4j platform.