How is it that I can go to bed at a certain weight and wake up the next morning at a lesser weight? Not complaining, just curious.

Insensible loss. Each day, just by breathing and sweating, we can expel up to 1.5 liters of water. A liter of water weighs 2.2 pounds, so we lose over 3 pounds of water a day. We don't notice it during the day while we are up and awake, eating and drinking, but while sleeping we can lose about a pound of water. And, if you evacuate your bladder during the night that another pound of water (400cc.)good luck.