Introduction

10.6% of people are left-handed. Handedness is the most obvious form of brain asymmetries in everyday life, i.e., functional or structural differences between the left and right side of the brain. However, there are many other forms of brain asymmetries, such as for language, emotions, and faces. This Essential provides an overview of the detection of left-handedness and brain asymmetries, as well as their evolution, development, and relevant animal  research. Other main topics include research on left-handedness and cognitive functions as well as the topic of handedness and sports. The Essential is rounded off with a discussion on the topic of relearning handedness and a discussion of altered asymmetries in various patient groups.