Exoplanet characterization: using interferometry and correlations Interferometry is a powerful technique to measure the angular diameter of stars, which is a key ingredient to infer all the stellar parameters. We will present this method and show its application to 18 stars (Ligi et al. 2012, 2016). From this, the planetary parameters can be deduced with a better accuracy. Furthermore, we will show how a careful use of correlations leads to a better estimate of the density of a transiting exoplanet. In Crida et al. (2018), we apply this to the case of 55 Cnc e, and we used Dorn et al. (2017)'s internal structure model to derive the physical parameters of this super-Earth (e.g. the thickness of its atmosphere). This method will soon be applicable to many other systems, and we will discuss prospects and insights about their formation.