Blood transfusions are regarded as the most well-known and frequently performed cell transplanta-tions.Although current transfusion systems are sophisticated,they cannot be freed from the inherent difficulties that include infection,short shelf life,and blood type mismatching.Artificial oxygen carriers produced using hemoglobin (Hb) are designated as Hb-based oxygen carriers (HBOCs),which are antic-ipated for use as biomaterials that have potential to resolve issues of transfusion by a radical paradigm shift.Various HBOCs,nanometer-sized to micrometer-sized bioparticles having an oxygen-carrying func-tion,are developed for use as substitutes for red blood cells (RBCs).This paper presents an overview of the classification of HBOCs with reference to their histories,preparations,structures,functions,and in vitro and in vivo properties.Additionally,we give a more detailed introduction of our academic studies of liposome encapsulated Hb,designated as Hb-vesicles (HbV),which mimic the physiologically important corpuscular structure of RBCs.This review outlines perennial efforts and approaches to mimic RBC func-tions through chemical,genetic,and encapsulation techniques.It will provide important insights into the eventual realization of an alternative for RBC transfusion.