The total energy produced by our sun during its entire lifetime is insignificantly miniscule compared to all the energy emitted by every star in the universe for a single nanosecond.
Depending on various theories of universe formation the universe could have a radius anywhere from at least 10x the observable universe to even infinite.
https://bigthink.com/starts-with-a-bang/galaxies-in-universe...
Ofc they are smaller, so its a classification problem.
It's called the heat death of the universe.
https://en.wikipedia.org/wiki/Timeline_of_the_far_future
This is assuming the cosmic concordance model describes reality. There are other models where some sort of reverse expansion will occur. They call it either Big Crunch or Big Bounce.
One neuron might seem insignificantly miniscule, but just one neuron may encapsulate you recognizing a specific face of someone important to you.
[1] https://bionumbers.hms.harvard.edu/bionumber.aspx?id=106322