The Center of Immune Deficits (CEDI) at Necker-Enfants malade Hospital is a laboratory of immunology and genetics whose the activity focuses on the diagnosis of inherited immunodeficiency diseases and the study of their immune reconstitution after treatment. The Laboratory of Cell and Gene Therapy (LTCG), Department of Biotherapy at Necker-Enfants malade Hospital has expertise in immuno-hematology and innovative therapies. The LTCG supports clinical trials of cell and gene therapy for inherited diseases by targeting hematopoietic cells. Flow cytometry is an essential and indispensable part of CEDI and LTCG which allows to diagnosis, follow-up of post-gene therapy patients and the quality control of advanced therapy products.