All physicists know that light carries both linear and angular momentum. What is perhaps less well known, however, is that its angular momentum can be broken down into spin and orbital components. Spin angular momentum is associated with polarization, whereas orbital angular momentum arises from a more complex combination of the phase and amplitude profiles of an optical field. Although the spin momentum is the predominant property used in optical-based quantum information applications, orbital momentum is potentially more powerful for encoding and processing such information in high-dimensional quantum spaces. In this issue, Gabriel Molina-Terriza and colleagues review progress in the generation, understanding and use of the orbital angular momentum of light.

[Progress Article p305]