The past few decades have seen the advent of multiple molecular imaging tools for the study of problems in the life sciences - often documented with stunning pictures. Not all problems in the living system, though, can be tackled using microscopy. I will provide at least two examples where it was the marriage of maths and physics that was used to tackle successfully a long standing problem in the life sciences - one involving oxygen delivery to red blood cells; the second involving movement of materials between circulating blood and metabolizing tissue.