The concept of squeezing is intimately related to the idea of vacuum fluctu ations, once thought to place an absolute limit to the accuracy of measure ment. However, vacuum fluctuations are not unchangeable. By recognizing that these quantum fluctuations always occur in two complementary observ ables, physicists have been able to make an intriguing trade-off. Reduced fluctuations in one variable can be realized - at the expense of increased fluctuations in another, according to Heisenberg. This Heisenberg 'horse-trade' - originally predicted by theorists - was first accomplished...