better understand their formation and evolution by comparison with the Solar System. In the course of his career, he developed new astronomical equipment, novel observational approaches, and detection algorithms. He participated and conducted programs leading to the detection of hundred planets, including breakthrough results. Early in his career, he identified stellar activity as a potential limitation for planet detection. He published a reference paper describing how to disentangle stellar activity from a planetary signal using proxies, including new algorithms that have become standard practice in all planet publications based on precise Doppler spectroscopy data. With this work he set the foundation to optimize measurements of stellar radial velocity that is still in use today. Queloz received the 2011 BBVA Foundation Frontiers of Knowledge Award of Basic Sciences (co-winner with Mayor) for developing new astronomical instruments and experimental techniques that led to the first observation of planets outside the solar system. Shortly after the start of the ELODIE planet survey at OHP, he led the installation of an improved version (CORALIE), on the Swiss 1.2-metre Leonhard Euler Telescope. Very quickly this new facility started to detect exoplanets on stars visible in the southern hemisphere. In 2000, he took the responsibility, as a project scientist, in the development of HARPS, a new type of spectrograph for the ESO 3.6m telescope. This instrument commissioned in 2003 was about to become a reference in the business of precise Doppler spectroscopy. HARPS performances, allied with the development of a new analysis software inherited from all past experiences gathered with ELODIE and CORALIE, would considerably improve the precision of the Doppler technique. Eventually, it would deliver spectacular detections of smaller exoplanets in the realm of Neptune, super-Earth systems before Kepler would massively detect them and establish their statistic occurrence. After the announcement of the detection of the first transiting planet (in 1999), Didier Queloz's research interest got broader with the objective to combine capabilities offered by transiting planets and follow-up Doppler spectroscopy measurements. In 2000 he achieved the first spectroscopic transit detection of an exoplanet using the so-called Rossiter-McLaughlin effect. This type of measurement essentially tells us about the projected angle between the stellar angular momentum vector and the planet orbital angular momentum vector. The pinnacle of this program would be reached 10 years later, after he led a significant upgrade of CORALIE, and established a collaboration with the Wide Angle Search for Planets (WASP) consortium