The characterisation of the thermal properties (thermal conductivity, thermal diffusivity) of complex heterogeneous solid materials at high temperature is not trivial and has been the subject of developments for many years at the Lemta laboratory. Over the years, measurement techniques have been developed and implemented using inverse methods adapted to increasingly complex materials and/or extreme thermal conditions where the heat transfer modes are strongly coupled. The Lemta’s experimental plateform is equipped with several spectrometers, microscopes, laser sources, infrared cameras, a fast multispectral camera, black bodies, a DSC calorimeter, furnaces and many other characterization benches. This plateform is in continuous development to extend the laboratory know-how in order to move from high temperatures (above 1000°C) to very or ultra-high temperatures (beyond 1500-2000°C). More specifically, in Lemta there is a bench for high temperature thermal characterization using the flash method and a bench dedicated to the measurement of insulating material thermal conductivity using the three-layer method in a vacuum chamber. At the heart of the current research works, in the context of the running joint CNRS laboratory Canop´ee, a new measurement bench was recently developed to measure the thermal properties of insulating materials with the hot wire method up to 1600◦C. Furthermore, there a measurement bench under development dedicated to temperature and emissivity estimation by multi and hyper-spectral methods on opaque and semi-transparent materials up to 2000◦C. In direct link with these measurement benches, analytical and numerical models are developed associated to inverse methods to elaborate diagnostic tools (fault detection, non-destructive testing etc.). The current and further development on this measurement field in Lemta aims to constantly improve the estimation of heterogeneous materials and complex energy systems thermal properties. They also aims to meet the challenges of measurement on high or ultrahigh temperatures. Direct and inverse coupled models are developed to take into account the interactions between the tree heat transfer modes.