The smallest thing in the world, as understood by modern science, is generally considered to be elementary particles - the fundamental building blocks of matter that are not made up of anything smaller.

Smallest Things in the Universe

1. Elementary Particles

• These include particles like quarks , electrons , and neutrinos.
• Quarks combine to form protons and neutrons.
• Electrons orbit the nucleus of atoms.
• These particles are considered point-like with no known size-they are treated as having zero dimensions in the Standard Model of particle physics.

2. Planck Length

• The Planck length (~1.6 × 10⁻³⁵ meters) is theorized to be the smallest meaningful length scale in the universe.
• Below this scale, the concepts of space and length may lose their usual meaning due to quantum gravity effects.
• It is not a physical object but a fundamental limit in physics.

Summary

• The smallest physical entities are elementary particles like quarks and electrons.
• The smallest meaningful scale in physics is the Planck length, beyond which space-time itself might be fundamentally different.

If you want to explore more about quantum physics or the nature of the smallest things, feel free to ask!