Cells in the deepest layer of your epidermis divide nonstop, then travel toward the surface, filling with keratin and dying along the way. At the top, they form a barrier of dead cells that eventually flakes off. The full cycle takes about four weeks in adults, longer with age. You shed tens of millions of cells a day.
Every day, your kidneys filter around 180 liters of blood plasma, about a bathtub's worth. Yet you only have about 3 liters of plasma, so it passes through your kidneys some sixty times a day. Over 99% of the filtered water is reabsorbed, leaving just one to two liters of urine.
A 70 kg adult is made of about 7 × 10²⁷ atoms, or seven billion billion billion. The observable universe is thought to hold on the order of 10²² to 10²⁴ stars. Even with the high estimate, you contain thousands of times more atoms than there are stars in the entire visible cosmos.