The phrase "a tiny grain" is correct and usable in written English.
It can be used to describe a very small particle or amount of something, often in a literal or metaphorical context.
Example: "She added a tiny grain of salt to the recipe to enhance the flavor."
Alternatives: "a minuscule particle" or "a small speck".
And yes, that premise probably contains a tiny grain of truth.
He insists that he will work only for winners, but a tiny grain of idealism remains deep in his heart, along with a sense of shame.
Understanding the past also has the benefit of making you feel different: more open, more like a tiny grain of sand on an enormous beach of time.
Experts are probably right to sound the alarm on the amount of time that children spend with digital devices, but the good-humored Mr. Garner may safely take their warnings with a tiny grain of salt.
A colleague, Vincent J. Schaefer, discovered that a tiny grain of dry ice produced many millions of ice crystals when dropped into a cloud of water droplets below the freezing point.
(He muses that there may have been a tiny grain of truth in the team's tongue-in-cheek motto, "Study to pass, race to win"). Wren also marveled at the sport's strategic nuances, which he learned by dissecting VHS tapes of pro races.
At best, a miasma of fetid lies cloaking a single tiny grain of partial truth.
As a million tiny grains pelleted the floor like rain, my child's eyes welled up with tears.
When people such as Soucy call to request the mailing address, a representative sometimes reminds them that: "You can't get your money back" and "You know, each American would have to pay about $52,000 to get us even" and "This is a little like picking one tiny grain of sand off the beach".
Perhaps because modernity has left Jordan alone, you can gaze at a forlorn bank building and tiny grain elevator and see faded storefront advertisements for Sioux City Sarsaparilla and the long-defunct Sellman's Motel.
Along one of those paths is a tiny old grain mill, and beside that is a ramshackle pharmacy, most of its shelves empty of everything but dust.
