The most elegant experiment in physics

Thomas Young's 1801 double-slit experiment.

Click the Molecular Expressions graphic below to see why Young's experiment was so profound.

Elegant indeed

An important version of this experiment involves single particles (or waves—for consistency, they are called particles here). Sending particles through a double-slit apparatus one at a time results in single particles appearing on the screen, as expected. Remarkably, however, an interference pattern emerges when these particles are allowed to build up one by one (see the above image). 

Quantum weirdness indeed. :)

Had to add a live version of the image seen above and ... there is no objective reality. :)