{ 1 } - states of affairs as being ultimately composed of simple objects that somehow fit together.
{ 2 } - complex statements as being ultimately analyzable into simple statements about simple objects.
{ 3 } - statements and facts as having a similar structure.
{ 4 } - all of the above.

Both statements and the facts that they represent can be analyzed into simpler and simpler components. The simplest statements and facts are about simple objects.

Unfortunately, Wittgenstein didn't give us any examples of these simplest statements. Some suggest examples like "I sense redness" or "This rock is next to that rock" or "This atom is moving toward that atom."