TREMO is a compact magnetic climbing inchworm with the capability to move in complex ferromagnetic environments. The robot fits inside a cylinder of 500 mm in height and 120 mm in diameter for an approximate weight of 800 g. It has a modular configuration based on three energy autonomous sub-systems: an arm and two feet. The arm has five degrees of freedom. It has a central articulation with a stroke of 270°. Both ends of the arm have an innovative articulation based on a differential system. This allows unlimited rotation of 360° in the heading angles and 180° in the elevation angle. At both ends of the arm a camera is mounted. The feet are donut-shaped and are mounted around the camera. The climbing ability is based on the advantageous properties of Magnetic Switchable Devices (MSD) [1]. Each feet of the robot embeds three MSD for better compliance and stability of the adhesion to the surface. The three MSD of one feet together with their motors weight 32 g and can hold above 90 N.