The main work of our research group is generation of genetically modified marmosets using lenti-viral vector method which we have successfully established in 2009. The genetically modified marmosets are an important tool for clarifying the higher brain functions of humans and some primates, such as the use of languages and tools. Our research group aims to establish methods of generating (1) target-gene-knockout marmosets (in which the functions of a target gene are made nonfunctional; the generation of such marmosets using lenti-viral vectors has been difficult) and (2) target-gene-knock-in marmosets (in which the site and time of target-gene expression can be monitored from the fluorescence of implanted fluorescent proteins such as the green fluorescent protein (GFP) in the target gene). In addition, we plan to demonstrate the effectiveness of these marmosets as a higher-brain-function model animal by carrying out embryological research on marmosets essential for our research.