This paper describes basic principles and techniques involved in designing waterproof breathability fabrics. Breathable fabrics are available in a large variety, which can be categorized as โ closely woven fabrics, microporous membranes and coating, hydrophilic membranes and coating, combination of microporous and hydrophilic membranes and coating, use of retroreflective microbeads, smart breathable fabrics and fabric based on biomimetics. Basic principles and mechanisms of water vapor transmission solely depend on the type of breathable fabrics. The formulation and application of microporous and hydrophilic membranes and coatings have been well researched in different fields of application. Smart breathable fabric and fabric based on biomimetics, which are of recent origin, are also showing their potential. The technology is continuously evolving in the areas of a cost-effective manufacturing process, improving material formulation to enhance the film's properties, and controlling pore sizes and their distributions, developing improved monolithic film and coating materials for a variety of applications. Method of incorporation of membrane, coating techniques, fabric substrate, lining material and above all the garment construction are also undergoing changes and play vital role in designing breathable garments.