This ebook is developed for understanding the CBC histogram in varous pathological condition. The CBC is a routine investigation of haematology, CBC strip include plotting of WBC, RBC and Platelet counts as well as their histograms. In cases of pathological affected blood samples the counts are usually false, in such situation plloted WBC, RBC and Platelet histograms are very helpful in diagnosis and interpretation of lesion/disease prior to smear examination.