We just learned about the Dorsal Venous Network of the Hand
The veins on the bottom or palm side of your hand are called the Superficial Palmar Venous Arch.
These veins are much smaller and can't really be seen from the skin, but they are right up along the arteries in the palm.
(from: wikipedia - superficial palmar venous arch)
Kid Facts - Blast from the past: Capillaries