Quarks, which we also cannot see, are a model to explain the properties of the protons and neutrons in the nucleus of an atom.

夸克同样看不到，但它却是解释原子核中质子、中子性质的理论模型。

youdao

She also shows how the chemical Luminol can reveal hidden blood stains that the eye alone cannot see.

VOA: special.2010.05.05

It might, possibly, create 67, 000 that we can see, but it will also destroy some unknown number that we cannot see.

FORBES: If Apple Onshored iPad Production it Would Create 67,000 American Manufacturing Jobs!

That instant coffee I was forced to buy out of a vending machine (see how I suffered?), also not deductible: you cannot deduct the cost of meals that are not part of inpatient care.

FORBES: Paying For Getting Better: What's Deductible?