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One view of what triggers star formation has been that self-gravitating clouds are supported against collapse by magnetic fields, with gravity-driven ambipolar diffusion reducing support in cores and hence triggering star formation. A newer paradigm is that magnetic fields are too weak to play this dominant role, and that damping of turbulence together with external triggers such as supernovae dominates. The crucial issue is the strength of magnetic fields in regions of star formation. Only observations of magnetic fields can settle the issue. This talk will review the techniques for measuring magnetic field strengths and morphologies in star formation regions, including a critical evaluation of the limitations of the various techniques. Then the current state of observations of magnetic fields will be reviewed, and the conclusions that can be drawn will be presented. Finally, the future will be discussed. This will include the advances that should come from new instrumentation, such as SCUBA2, CARMA, and ALMA, as well as a new observational test - the direct measurement of the differential mass to magnetic flux ratio between cloud envelopes and cores. This measurement eliminates most of the biases generally present, and should provide a direct test for ambipolar diffusion. The feasibility and time scale of the proposed new test will be discussed.
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