Albert Michelson and Edward Morley performed the Michelson-Morley Experiment in 1887 by splitting a beam of light in two sending in two directions to measure by interference the difference in the transition of the two beams. It is considered the first strong evidence against the theory of a luminiferous aether helping lead to the development of Special Relativity.
Controlled Experimentation is fundamental to the ideal of science. It is where the scientific method and repeatability works best. However not all area of scientific study lend them selves to experiments. Most real world observations are beyond the possibility of a controlled experiment do to things like distance, size and time. In many case experiments can only be used to test the possibility of a hypothesis which is some times done in historical sciences. Trying to replicate a past event to show it could have happened.
The Ideal Experiment should reduce the number of variable to one and be easily repeated by other scientists to increases the likely hood that someone will try to repeat it. It also makes it more likely that the attempt to repeat it will succeed. It should also limit complexity and cost so as to increase the likely hood that someone will try to repeat it making it more likely that the attempt to repeat it will succeed.