Each hair follows its own cycle: a growth phase lasting 2 to 7 years, a pause, then shedding, before a new one grows from the same follicle. Because these cycles are staggered, you lose 50 to 100 hairs a day without thinning. The length of the growth phase also sets how long your hair can ever get.
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.