The notion of each atom containing another smaller universe is not a scientifically supported concept or a widely accepted theory within the field of physics or cosmology. As far as our current understanding of the universe goes, there is no evidence or theoretical framework that suggests that each atom contains a smaller universe within it.
In the context of our known universe, its size is vast and difficult to comprehend. The observable universe, which is the portion of the universe we can potentially observe from Earth, is estimated to have a diameter of about 93 billion light-years. This observable universe encompasses an immense number of galaxies, stars, and other celestial objects.
It's important to note that the term "universe" typically refers to the entirety of all space, time, matter, and energy. It encompasses everything we can possibly observe, including galaxies, clusters of galaxies, cosmic structures, and the space between them.
While the size and nature of the universe are still active areas of scientific exploration and investigation, there is no evidence or scientific basis to support the idea that each atom contains smaller universes. Our current understanding suggests that the universe we observe is a single, vast entity on a grand scale.