Given mass, radius, and equilibrium temperature, ExoMDN can deliver a full posterior distribution of mass fractions and thicknesses of each planetary layer. A machine-learning model for the interior characterization of exoplanets based on Mixture Density Networks (MDN), ExoMDN is trained on a large dataset of more than 5.6 million synthetic planets below 25 Earth masses. These synthetic planets consist of an iron core, a silicate mantle, a water and high-pressure ice layer, and a H/He atmosphere. ExoMDN uses log-ratio transformations to convert the interior structure data into a form that the MDN can easily handle.