Meng Jin studies the morphology, systematics, and evolution of mammals, particularly early mammals. Unlike some paleontologists who focus primarily upon teeth and dentition as their evidence, Dr. Meng examines the cranium, ear region, and enamel microstructure of teeth as sources of data to address evolutionary issues concerning mammals. He uses digital imaging, radiography, scanning electron microscopy, and computerized tomography to enhance observations and field work. Most of Dr. Meng's fieldwork takes place in Asia-primarily in Inner Mongolia, Xinjiang Province in northeast China, and southern China. Dr. Meng has done research on several mammal groups including didymoconids, multituberculates, and gliriforms. Most recently, Dr. Meng and his colleagues published research on a fossil of a 130-million-year-old opossum-sized mammal, Repenomamus robustus, found with the remains of a psittacosaur in its stomach area. This fossil is the first direct evidence that some primitive mammals were carnivores and fed on small vertebrates, including young dinosaurs.