The Uncertainty Principle which was published by Werner Heisenberg in 1927 was based on the fact that the light needed to observe a subatomic particle will disturb it making measurements uncertain though it goes beyond that.
FormulaDX DP ³ h/4p
X = The particles position
P = The particles momentum
Planck's constant - h = 6.626 X 10-34 J * S
Planck's constant is too small for the uncertainty principle to show up in the macroscopic world but it is significant in the subatomic world nut it results in the fact that the more accurately one measures a particle's position the less accurately one can measure its momentum and one measures a particle's momentum the less accurately one can measure its position. This does not happen just because the act of measurement disturbs the system; which it only does sometimes; it is actually related to Wave-particle duality. The same principle applies to other quantities like energy and time.
There has been a more recent development involving the debate between determinism and freewill. The idea is that the uncertainty principle is a possible avenue for allowing for freewill in neurology. The evidence involves quantum, mechanical processes like tunneling being involved in synapse activity.
The Uncertainty Principle shows us that we are limited in our ability to make measurements of the subatomic world. It shows that there are limits to our possible knowledge about the universe.