nuance-subtle

Now I want to stress one other nuance here.        
这里我还想强调另外一个细微的差别。
微小的 subtle 注意b不发音
For that reason, subtler chemical assistance is still worth pursuing.        
因此，更不易察觉的化学道具仍值得研究。

a very slight difference in meaning, sound, colour or sb's feelings that is not usually very obvious
He watched her face intently to catch every nuance of expression.
他认真地注视着她的脸，捕捉每一丝细微的表情变化。