  In this white paper, we present a cross-section of important scientific
questions that remain partially or completely unanswered, ranging from Titan
exosphere to the deep interior, and we detail which instrumentation and mission
scenarios should be used to answer them. Our intention is to formulate the
science goals for the next generation of planetary missions to Titan in order
to prepare the future exploration of the moon. The ESA L-class mission concept
that we propose is composed of a Titan orbiter and at least an in situ element
(lake lander and/or drone(s)).
