In the past, determination of bone maturity relied on visual evaluation of skeletal development in the hand and wrist, most commonly using the Greulich and Pyle atlas. The Gilsanz and Ratib digital atlas takes advantage of digital imaging and provides a more effective and objective approach to assessment of skeletal maturity. The atlas integrates the key morphological features of ossification in the bones of the hand and wrist and provides idealized, sex- and age-specific images of skeletal development. An important new feature of this revised second edition is the inclusion of a description and user manual for an iPhone/iPad App that can be purchased and used separately from the book. The App can be easily employed to calculate the deviation of the patient's age from the normal range and to predict a possible growth delay. This easy-to-use atlas and the related App will be invaluable for radiologists, endocrinologists, and pediatricians and also relevant to forensic physicians.