The spherical torus (ST) machine has recently emerged as an innovative example of fusion confinement that could allow progress to be made in fusion energy development. For example, experiments are conducted with spherical tori to establish the physics principles of the low aspect ratio. Although the ST plasmas are similar to the standard aspect ratio tokamak plasmas in many ways, the range of physics parameters can lead to important new plasma behaviours such as increased stability. In addition, creating plasma in spherical tori reduces transport because of the flow shear and geometric configuration.