Scientists classify cells into two categories. lack a nucleus and other membrane-bound organelles, while have a true-nucleus and complex, internal structures that are also membrane-bound.

for example, no new evidence will demonstrate that the earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the earth is not divided into solid plates that have moved over geological timescales .