There are two ways of getting energy from nuclei.
So me nuclei can break apart to release energy. This is
called fission. Other nuclei can be put together to make
a new nucleus, while giving out energy. We call this
process fusion. Fission and fusion are different
processes, but both produce enormous amounts of
energy due to reaction. Fission is a simpler process
than fusion, and was discovered earlier. The difficulties
of controlling fusion to generate usable power have not
vet been overcome. Today fission is still the main
method of producing nuclear energy.