Gaseous detectors like TPCs are seldom used in Rare Event searches (like those looking for Dark Matter particles, Neutrinoless Double Beta Decay or other neutrino experiments) due mainly to the difficulty in reaching target masses large enough to be sensitive to the extremely low counting rates expected. However, very promising recent advances in TPC readouts based on micropatterns (e.g. the Micromegas concept) may overcome those limitations, making the application of TPCs to this kind of experiments not only viable, but competitive. The first order discoveries that await us in double beta or dark matter experiments will require the identification of the signal events with an unmistakable signature like the one only offered by gaseous detectors. The proposed research aims at the exploration of these new concepts from the point of view of low background techniques, and at their development up to the point of application to next-generation high-discovery-potential experiments in this field. The main practical objective is the creation and consolidation, in the host institution, of a core of technological and scientific expertise on TPCs for low background applications. In addition, the host group is currently responsible for the maintenance and operation of the new Canfranc Underground Laboratory (LSC). The proposed development will have high impact regarding future experiments in the field. In particular, they will find direct application in several starting initiatives in which the applicant has a leading role: the recently proposed Neutrino Xenon TPC project (NEXT) for double beta decay at Canfranc, the Cosmology with Nuclear Recoils (CYGNUS) network to explore the directional signal of Dark Matter particles and, more generically, the CERN-based RD-51 technological collaboration recently approved to promote developments on micropattern detectors. It will certainly have practical applications beyond fundamental science.