A PhD usually focuses on depth because you need to find new results, which usually isn't possible with breadth alone. A nice visualization: http://matt.might.n

A PhD usually focuses on depth because you need to find new results, which usually isn't possible with breadth alone. A nice visualization: http://matt.might.net/articles/phd-school-in-pictures/ http://matt.might.net/articles/phd-school-in-pictures/