Fission is the type of nuclear energy simulated on Earth, as it is the one used to generate electricity. Fusion, on the other hand, is much more complicated to achieve because it requires extremely hot temperatures compared to fission. Fusion involves the combination of two hydrogen atoms to make helium, which releases a lot of energy. Stars such as the sun, exhibit fusion with its very hot temperature and abundant source of hydrogen.
Molecules make scents. Aromatic ones (That is, containing rings of carbon atoms with delocalised electrons). Some unpleasant smells are due to hydrogen and sulphur groups.