Kidney tubule cell, coloured scanning electron micrograph (SEM). This cell (blue) is covered in thin projections (microvilli) that serve to increase its surface area. This aids its function, which is to reabsorb water and small molecules from urine, concentrating it. The liquid in the tubules passes to the bladder for urination, while the reabsorbed water and other molecules are returned to the bloodstream. Magnification: x6500 when printed 10 centimetres wide.