Advances in conventional cancer treatments such as chemotherapy and radiotherapy have provided vast improvements in cancer survival rates over recent years. However these techniques inevitably lead to the damage of some healthy tissue and cells, resulting in harmful side effects. Many researchers around the world are therefore working to develop targeted cancer therapies that are tumor-specific, and so destroy cancer cells without affecting surrounding healthy tissue. One such technique, known as hyperthermia, uses heat sources to induce cancer cell death by transiently raising the local temperature in the tumor to above 42 deg C. However, generating local heating in a controlled and non-invasive fashion is difficult with conventional techniques. An alternative method is to use magnetic hyperthermia (or 'thermotherapy') which is an experimental cancer treatment that uses microscopic magnetic particles (nanoparticles) that are only 1/5000th of the width of a human hair. These nanoparticles can channel the energy from an external high-frequency alternating magnetic field in order to create local hot spots. As heating can only occur where nanoparticles are present, the technique is truly local and effects can be obtained by accumulating nanoparticles within tumors. Magnetic hyperthermia has produced encouraging results that show it can reduce the size of tumors, and in recent clinical trials where it was combined with radiotherapy, a significant effect on cancer survival times was reported. However these results were achieved by dispersing very concentrated magnetic nanoparticle fluids around the tumor. Although this represents local heating of the tumor, in order to prevent the cancer from spreading it is essential to kill each and every cancer cell, and so a cellular level heating effect is required. Much work has therefore focused on labelling individual cancer cells with magnetic nanoparticles, either by binding them to cell membranes or by allowing them to be engulfed by the cells. In principle these particles should then be able to heat the cells directly to trigger cell death. However the results of such experiments to date have been somewhat disappointing because it seems the magnetic and heating properties of the nanoparticles can change once they are associated with cells. In order to understand this behaviour it is first necessary to be able to probe the properties of the nanoparticles in real cellular environments, and to see how these vary depending on the microscopic location of the particles, i.e. where they reside inside or externally to cells. The ability to make such measurements would enable a systematic evaluation of how the design and location of the nanoparticles, as well as the magnetic field conditions used, could favourably enhance the magnetic properties and consequently the cellular level heating. Such a study would dramatically boost research on magnetic hyperthermia, taking it much closer to realisation as a viable clinical therapy. However at present no such instrument exists in order to perform this work. Therefore the aim of this project is to create a new type of microscope that can probe both the magnetic and heating properties of nanoparticles in cellular environments. This will be done by exploiting the magnetic dependence of certain optical phenomena, such as the well-known Faraday effect, and combining them with specialist fluorescence based techniques to measure local temperature. As the various components of the instrument take shape they will be used to evaluate the performance of a range of bespoke nanoparticles in order to understand how sufficiently strong cellular-level magnetic hyperthermia effects can be achieved. We are confident that the new instrument produced in this project will provide the step-change advancement required in nanoparticle evaluation to enable magnetic hyperthermia to be a viable and essential technology in the fight against cancer.