Low energy transfers to the Moon were first demonstrated in 1991 by the Japanese spacecraft Hiten. This was a result of a mission rescue by Edward Belbruno and James Miller. The transfer used by Hiten is a revolutionary new type of low energy transfer to the Moon derived from Weak Stability Boundary Theory. See Capture Dynamics and Chaotic Motions in Celestial Mechanics Unlike the standard three day transfer to the Moon this low energy route does not require large rocket engines to slow down to be captured into lunar orbit. It also takes three months instead of three days.
Low energy transfers follow special pathways in space, sometimes referred to as the Interplanetary Transport Network. Other missions that have used low energy transfers are SMART-1, of the European Space Agency, and Genesis, of NASA.