Cilia are small hair-like protuberances on the surface of cells. They are divided into two groups, motile and immotile primary cilia. Motile cilia are primarily responsible for locomotion of fluids on the cell surface. Primary cilia are also involved in mechanoreception. Among motile cilia, airway (nasal and bronchial) cilia are involved in elimination of inhaled viruses (such as SARS-CoV-2), pathogens, and particles entrapped in mucus layer out of the body (mucociliary clearance) as one of the important biological defense systems. Ependymal cilia are involved in cerebrospinal fluid flow. Any abnormality or defect occurring in the structure and movement of cilia results in primary ciliary dyskinesia, the symptoms of which include sinusitis, bronchitis, infertility, hydrocephalus and Situs inversus. Our laboratory is conducting research using human primary culture systems and model animals, in elucidating the development of airway and ependymal cilia and regulation mechanism of their movement and attempting to discover potential seeds of new drugs.