Final answer:
The universe's structure has evolved from smooth early conditions to complex formations. Depending on the overall mass and energy density, it may continue to expand or eventually contract in a 'big crunch.' Superstring theory implies a finite lower limit for the size of any object in the universe.
Step-by-step explanation:
According to cosmological models, the structure of the universe evolved from small disturbances in the early universe that grew over time due to gravity. The growth of large-scale structures like filaments, galaxies, and superclusters, as simulated by supercomputers, reveals the transition from a relatively uniform distribution to the complex structures we see today. If the density of the universe exceeds the critical density, there is a possibility, in a closed universe scenario without dark energy, that it will eventually stop expanding and begin to contract, leading to the so-called 'big crunch.' On the other hand, at the critical density, the universe can continue to expand forever. Superstring theory suggests a finite lower limit to space, indicating a smallest possible size for objects.