Why it is that the space within our minds "feels" almost as expansive as the space without? In some ways it is even more so. Inside, we really can, imaginatively speaking, "go where no man/woman has gone before," while the physical world limits our options in a much more dramatic fashion.
The number of cells in the human body? Some scientists estimate they number about 10 to the 14th power. That is, about 100 trillion. And how many trillions of trillions of subatomic particles are these cells comprised of? The observable universe itself contains an estimated 80 billion galaxies, made up of somewhere between 30 to 70 sextrillion (1 sextrillion = 6 trillion) stars. The number of atoms in the universe is estimated to be at least 10 to the 80th power.