The US suffered huge economic damage from a microscopic amount of agent.

A microscopic amount of an allergen is introduced to a patient's skin by various means:

The technician measures the microscopic amount of water absorbed on freshly broken surfaces.

The sopapillas were good, and the honey wasn't bad in small, nay, microscopic amounts.

Trace elements, even in microscopic amounts, do funny things to the biochemical balance.

Today Lahoud had only a microscopic amount, just enough to prove he could bring more.

This meant microscopic amounts of meat, only for the very rich, and a vegetarian diet for the rest.

The term bulk in this context means a statistically significant quantity of particles (which can be a microscopic amount).