Usage: all types of cells and microorganisms (originally designed for blood cells) Depth : 0,1 mm Grid size : Grid of 3x3 mm. Subdivided in (3x3) 9 big squares. Each big squares in subdivided in (4x4) 16 medium size squares. The central square is specially designed for counting small particles. It is divided in (20x20) 400 small size squares of 50 microns.