In our modern world, very few mysteries remain. We can measure the distance from the earth to the stars, and explain the voids between. We can travel to the bottom of the darkest oceans, and reveal their secrets. We can see inside our own bodies, our veins, our cells, and we can even know the sex of a baby long before it is born. Little wonder, then, that when we ask ourselves, 'How much milk is my baby getting?', and we can't provide an answer, we find this disconcerting, to say the least. Breast milk, and in particular, the quantity that has left our own body and is now residing happily in our baby's stomach, is difficult to measure. We might try pumping, so that we can see how many millilitres we can produce, but this does not give any real indication of how much our baby is actually getting out. Not only are babies mouths unsurprisingly more efficient than a plastic sucker, but the actual loving act of nursing and looking down at our babies fac...