Your fingerprints form before birth, roughly between the 10th and 17th week of pregnancy. Their pattern depends on genes, but also on tiny details: pressure from amniotic fluid, the fetus's position, how fast each finger grows. So even twins with nearly identical genomes end up with different prints.
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.