Uh, what...? You may be thinking of independent clauses, such as in this sentence:
Musashi, famous swordsman of the Edo era, is known for his two-bladed fighting style.
Here, "Musashi is known for his two-bladed fighting style" is the independent clause, and the descriptive phrase stuffed in the middle to round out the sentence ("famous swordsman of the Edo era") is the dependent clause. The independent clause is called such because it can be a sentence on its own without the fluff in the middle, so in a way I suppose that's a "sentence in a sentence".
you do Whats within that box!?
A quote which is incorporated within a sentence where it makes sense with the rest of the sentence.
"It is not within my purview to answer that question."
Yes, if the sentence is otherwise well written and it fits within the context of the paragraph.
A root sentence is another term to reflect the original part of the sentence structure. There are adjectives and adverbs to fill in spaces; but, the initial parts of the sentence is contained within.
The engineer will build a building, within this site.
you do Whats within that box!?
What does it mean to vary the sentence pattern within a written work?
Our guests will be arriving within minutes.
If there is an exclamation point or question mark within a sentence, the immediately following word is not automatically capitalized. It can be, however, but that would have to depend on the context.
To explain something within the sentence without finishing the sentence before explaining.
Within the dark cave... or something Within the prison walls there were many criminals.
A quote which is incorporated within a sentence where it makes sense with the rest of the sentence.
Underlining words within a sentence is one way to emphasize them.
You space between all words in a sentence.
The brain is within the human
No, a preposition does not have to be found at the beginning of a sentence. It can appear anywhere within a sentence, depending on the structure of the sentence.