After the farmers harvest the crops, they RE-USE the grain to plant next year's crops.
Rice grains, on the tops of the rice shoots, appear to be standing up facing the sun.
a grain,, for instance . . . rice
an atomic particle, as in 'particle physics.'
If you STAND on top of grain,
you'll grind it to powder in one MINUTE
STRING is too ambiguous to be a good mnemonic!