1.   As gravity tugs the cluster downward, it passes through a chamber filled with precisely tuned microwaves, which excite those atoms whose resonant frequencies match the microwave frequency.

2.   Chlorophyll A can also use solar radiation to excite atoms in the cells of the leaf, setting off a reaction that converts the light energy into chemical energy.

3.   It excites atoms to create light.

4.   The device uses a high-energy laser to excite atoms, which then can be identified by the unique spectra of the light they give off.