# Lightest object so far to function as gravitational lense?

Many amazing discovers are based on gravitational lensing and microlensing, but as non-expert it is not obvious to me:

What is the (current) lower mass limit of the lensing object(s) for which astronomers have been able to determine that the apparent position of an object behind it has been deflected or otherwise lensed gravitationally?

• +1 What are the "hypothetical so-called primordial black holes at 5 Earth masses"? Can you add a link? Is there some specific prediction about 5 Earth mass primordial black holes?