least little thing
The smallest, most trivial, or most inconsequential thing or aspect. She's so sensitive—the least little things seem to get her in a huff. My boss is such a perfectionist that he will halt production to scrutinize the least little thing he thinks could be improved.
least little thing
the smallest possible thing. He gets upset over the least little thing. When she was a girl, she would throw a tantrum over the least little thing.