Pathologist have been using microscopes to analyze tissues on glass slides since the early 19th century. In the 1990s, whole slide scanners producing high-resolution digital images from glass slides in a span of minutes were developed which led to the birth of digital pathology. These digital images are known as whole slide images (WSIs). The WSIs are analyzed by the pathologist using computer monitors instead of microscopes. The WSIs can be accessed anywhere/anytime through a secured network connection and makes collaboration with clinicians and colleagues easier. Digital pathology enables the development of computational toolsets to aid and improve the diagnostic work of the pathologists.