Shown is an immunostained chick spinal cord cross section. Rachelle Sauvé and colleagues used a technique called electroporation to introduce mutated β-arrestin (magenta) and a fluorescent protein that is expressed only in commissural neurons (green) into this chick as an embryo. This manipulation of the activity of β-arrestin, a scaffolding protein, was done to determine its role in commissural axon development. They found that the expression of mutated β-arrestin changed the trajectory of the axons of commissural neurons in the spinal cord. See the article by Sauvé et al. for more information on how they uncovered the necessary role of β-arrestin in axon guidance. Cover image: Steves Morin.