The 37 °C (98.6 °F) figure dates back to 19th-century measurements. Modern studies find an average closer to 36.6 to 36.8 °C, with real differences between individuals. Above all, your temperature shifts by around 0.5 °C over the day: lowest in the early morning hours, highest in the late afternoon.
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.