2018 saw France host a landmark event in the history of science: the redefining of the kilogram. There were also Nobel-winning advances in laser technology, and we'll soon be getting a feel for Martian vibrations, as scientists land a seismometer on the red planet. On 16 November in Versailles, the General Conference on Weights and Measures adopted a resolution to update the definitions of the International System of units based on fundamental constants of nature. This means that the kilogram, whose standard was a platinum iridium cylinder stored in a vault near Paris, will from now on be defined by Planck’s Constant. The year also saw a French scientist winning a Nobel Prize. Professor Gerard Mourou of Ecole Polytechnique won this year’s Prize in Physics (along with Professor Arthur Ashkin and Professor Donna Strickland) for developing a special laser technique with important applications in the fields of industrial machining, ophthalmology and particle physics. French scientists are also playing important roles in two space missions that were launched this year. First, a magnetometer developed by researchers from the University of Orléans, which is a part of the Parker Solar Probe (launched in August) that aims to study the nature of the Sun’s atmosphere. And Philippe Lognonné, of the Institut de Physique du Globe de Paris, who is the principal investigator of the seismometer instrument that will measure vibrations on Mars. The seismometer, part of the InSight mission that landed on Mars on 26 November, could reveal what lies beneath the Martian surface.