Hydrogen and helium are the simplest elements in the universe, and they're made up of just protons, neutrons, and electrons.

Here's a breakdown:

* Hydrogen (H):

* 1 proton: The defining characteristic of a hydrogen atom.

* 0 or 1 neutron: Most hydrogen atoms have just one proton and no neutrons (this is called protium). However, there are also isotopes of hydrogen with one neutron (deuterium) and two neutrons (tritium).

* 1 electron: This electron orbits the single proton in the nucleus.

* Helium (He):

* 2 protons: This is what makes it helium.

* 2 neutrons: The most common isotope of helium has two neutrons. Other isotopes exist but are much rarer.

* 2 electrons: These electrons orbit the nucleus, which contains the protons and neutrons.

So, while they are the most basic elements, they still contain these subatomic particles that give them their unique properties.