The transversus abdominis plane (TAP) block is a regional technique for analgesia targeting the spinal sensory nerves of the abdominal wall. TAP block was first described by Rafi in 2001, who used anatomical landmarks of the lumbar triangle of Petit and the “double-pop” technique (indicating passing the external and internal oblique fascia). The triangle of Petit is defined by the borders of the iliac crest, the latissimus dorsi and the external oblique, with its tip placed at the rib cage (see also ► Figs. 36.2 and 36.3 ) (Rafi 2001). Hebbard et al. introduced the ultrasound guided technique and changed the needle insertion point from the triangle of Petit to the midaxillary line (Hebbard et al. 2007). This interfascial plane between transverse abdominal and internal oblique muscles, or in the case of subcostal TAP block, between the transverse abdominal muscle (TAM) and the posterior sheath of the rectus abdominis muscle (RAM) accommodates the spinal sensory nerves of the abdominal wall, derived from the anterior rami of thoracolumbar nerves, Th6–L1 (◘ Fig. 9.1a) (see also ► Figs. 7.1 and 7.5 ). These branches communicate and build plexuses right above the transverse abdominal muscle, providing sensory innervation of skin, muscles and parietal peritoneum. Hence, targeting these nerves results in anterolateral abdominal wall analgesia but no visceral analgesia (Abdallah et al. 2013; Rozen et al. 2008; Carney et al. 2011).