What is jupiter, saturn, uranus, and neptune made of??

Well, Jupiter and Saturn are mostly comprised of Hydrogen and Helium.

Neptune on the other hand is made mostly comprised of Methane.

and Uranus is made of

Methane as well

Jupiter; hydrogen and helium

Saturn hydrogen and helium

uranus; water, methan, ammonia fluids

Neptune; hydrogen and helium and a little bit of methane.

Hope i could help :)