Tomographic processes for biomedical purposes has observed a fantastic development during the last few years, such as ultrasonic echography, X-ray tomodensitometry or NMR tomography and more recently active microwave imaging. This new modality offers a low spatial reslution, depending of the frequency, but, in some cases significant contrasts related to dielectric properties of tissues. The interpretation of microwave images presents some specific aspects related to the diffraction mode of interaction between microwave beams and tissues. Tomographic algotithms have been developped to compensate for such diffraction effects. More works are still needed to improve image quality in terms of spatial resolution or artefact delete. Initially, motivated by non-invasive thermal control of deep hyperthermia treatment, experiments have been conducted on phantoms with different heating modalities. This paper presents some results to evaluate spatial and thermal resolution capabilities of microwave tomography. More recently, to respect to contrast, more general applications have been investigated: detection of inflammatory processes, monitoring of lung water content changes,control of organs defrozing...Some prelimary results obtained with a 2.45 GHz planar microwave camera are presented.