The use of ultrasound is the latest major evolution in regional anaesthesia. Review of available literature shows significant changes in clinical practice. Ultrasound guidance allows the visualization of anatomical variations or unsuspected intraneural injections, reduces the volume of local anaesthetic injections and confirms correct local anaesthetic distribution or catheter placement. No study has found a statistical difference in success rates and safety because all studies were underpowered. However, the ability to visualize an invasive procedure that has been performed blindly in the past is an undeniable progress in terms of safety. The necessity to be familiar with the machine and the learning curve can be repulsive. The aim of this article is to demystify ultrasound guidance by explaining the fundamentals of the clinical use of ultrasound. With the help of different chapters, the authors explain the different adjustments and possible artefacts and give easy solutions for the use of bedside ultrasound. Training is essential and can be performed on manikins or training phantom. For each region the main anatomical landmarks are explained. One must be familiar with several imaging techniques: short axis (transverse) or long axis (longitudinal) nerve imaging, in-plane or out-of-plane imaging and hydrolocalization. Viewing the needle's tip position during its progression remains the main safety endpoint. Therefore, electrical nerve stimulation and ultrasound guidance should be combined, especially for beginners, to confirm proximity to neural structures and to help in case of difficulty. Optimizing safety and clinical results must remain a key priority in regional anaesthesia. Finally, specific regulations concerning the transducers are described. Paediatric specificities are also mentioned.