What are some of the theories about the infinity of the universe?

I was just wondering if scientists still believe that maybe the universe is infinate and what some of the other theories people have about what the universe is? Couldn't the universe be a part of something bigger? Couldn't we be inside a cell of an unimaginable organism beyond our comprehension? What are some of the biggest mysteries we are trying to solve in the scientific community regarding space, and do scientist believe we will ever find the truth to these mysteries? Im just a normal person asking questions I in no way have any preconcieved idealogy just curious any answer would be encouraged.