Minerva Foundation Institute for Medical Research 1 article published in JoVE Neuroscience Measuring Properties of the Membrane Periodic Skeleton of the Axon Initial Segment using 3D-Structured Illumination Microscopy (3D-SIM) David Micinski1, Lauri Lahti2, Amr Abouelezz1,3,4 1Minerva Foundation Institute for Medical Research, 2Department of Computer Science, Aalto University School of Science, 3HiLIFE - Neuroscience Center, University of Helsinki, 4HiLIFE - Institute of Biotechnology, University of Helsinki The present protocol describes a method to visualize and measure actin rings and other components of the membrane periodic skeleton of the axon initial segment using cultured rat hippocampal neurons and 3D-structured illumination microscopy (3D-SIM).