Final answer:
A hemocytometer grid typically contains several primary squares used for counting cells, with each having a volume of 0.008 mm³ or 0.000008 mL when using a Petroff-Hausser chamber.
Step-by-step explanation:
The hemocytometer grid typically contains several large squares, usually arranged in a pattern to form a larger square. Each primary square is used for counting cells in the sample. If using a Petroff-Hausser chamber, similar to a hemocytometer, each primary square has a known area and depth. Considering that the cover slip is 0.2 mm above the grid and the area of a square is 0.04 mm², the volume of each primary square can be calculated by multiplying the area of the square with the depth the cover slip is set above the grid. Hence, the volume of each primary square is 0.008 mm³ (0.000008 mL).