From the BBC:
Scientists have outlined how they managed to create a fusion reaction using a household microwave oven.
Nuclear fusion is a nuclear reaction in which two or more atomic nuclei collide at a very high speed and join to form a new type of atomic nucleus. During this process, mass is not conserved because some of the mass of the fusing nuclei is converted to photons (energy).
An Irish-UK team placed hydrogen and helium (used in party balloons) into a 800W microwave oven, then added water and dishwashing liquid, and left on full power for several hours.
The results are reported in the journal Nuclear For Beginners.