Thermonuclear reactions are the source of the sun's energy.

The use of nuclear bombs is one of the greatest threats to mankind.

He likes to take a walk in the park at dusk.

Groundwater pollution has become a serious environmental problem.

I went to the station through the underground passageway.

He is an expert in experimental psychology.

Research on cold fusion is still controversial.

The number of nuclear-armed countries is increasing worldwide.

The caudate nucleus is a part of the brain that plays an important role in motor control.

The amygdala is a part of the brain that controls our emotions.