It can be easy not to see the wood for the trees, particularly when looking at the human body. We focus too heavily on one organ, one cellular structure or a single biochemical reaction, when there is often a multitude of factors and a complex interplay of systems. To name but a few, the complexity of mind over body, hormonal molecular reactions, or the interaction between the body's cells and the organisms living within or on the body itself. This leads us to probiotics, the