This work deals with the kinematic conception and the mechanical design of ultra-high precision robots, which are at present costly to develop, both in time and money. The aim of this paper is thus to introduce a new modular concept of kinematics which allows to significantly reduce the time-to-market and a new double-stage flexure-based pivot. Regarding the modular concept of kinematics, this ‘robotic Lego’ consists in a finite number of building bricks allowing to rapidly design a high precision machine and to easily modify its mobility. The realised mock-up of a 4-DOF (Degrees of Freedom) robot, transformable into a 5-DOF one, validates this concept and the mechanical design of its bricks. Flexure hinges are used to achieve the aimed sub-micrometer precision; however, existing flexure-based rotary joints are not able to fulfil the requirements of some applications, as they present a too low angular stroke and a parasitic motion of their centre of rotation. Thus, this paper also introduces a new double-stage pivot based on blades working in torsion; experiments performed on a prototype allow to validate its principle and the simulation model used for its development.