That's the basic idea... look, there's only a very finite number of elements that can be combined to make a relatively small number of compounds from which all matter proceeds Even then, not all elements can be combined with just any old other element. The elements and therefore the compounds are made of atoms in certain combinations (H20 as water comes to mind). The atoms making up the human body are the same, constttuently, as those making up your referenced chair... The human body just has different ratio than does the chair. For clarity, it's important to understand that one example of matter can have atoms that another may not have... but if the example has, say carbon, as a basis, the atoms of carbon are the same... otherwise it wouldn't be carbon...