The specific growth direction of plant cells is determined to a large extent by the orientation of what are known as 'microtubules' in the cells. These sturdy little tubes of tubulin proteins form a highly-ordered structure perpendicular to the direction of growth. Researchers at the Foundation for Fundamental Research on Matter’s Institute for Atomic and Molecular Physics (FOM AMOLF) have shown how this structure organizes and maintains itself. Although the tubes can grow and shrink in all directions, a form of Darwinian selection takes place. Read more