The intent of this work is to provide on-line access to images that are characteristic of a wide array of hematological disorders and other disorders that affect the blood, enhancing written descriptions found in Williams Hematology and other relevant medical books published on-line by McGraw-Hill. This Atlas permits an extensive presentation of blood, marrow, lymph node, spleen, and other organ pathology that would be too costly to be included in the print version of the text.