What are Square Microinches?
A square microinch is the area of a square one microinch (a millionth of an inch) on each side, so it is one trillionth of a square inch (10⁻¹²). In metric terms that is about 0.00064516 square microns.
What are Acres?
An acre is 43,560 square feet, which is about 4,047 square meters. It was originally the amount of land a yoke of oxen could plough in one day.
The United States and United Kingdom still measure land in acres, but most of the world uses hectares, which fit neatly into the metric system. One hectare is about 2.47 acres.