Our oral cavity is always exposed to various microbes yet we rarely get diseases.The reason behind is human innate immune system which is the gift of nature and need of the hour. Neutrophils are white blood cells which proved to be the first line of defence in our oral cavity.These are the most abundant white blood cells commonly called as 'Polymorphonuclear cells' occupying 60% of the immune cells of our body. This book clearly explain the scientific concepts and dramatic working mechanism behind these defence cells mainly in the field of periodontology.