Stable isotopes can yield powerful insights into the ecology of animals, providing windows into ecological processes that we cannot usually observe. But, like many methods, they are prone to misuse and misinterpretation. Seemingly simple patterns do not always give us the ecological insights that we think. The patterns that we see are the emergent property of complex interactions involving physiology and ecology, and patterns might be due to physiological influences. This talk will show how understanding physiology, chemistry, anatomy and ecology can help refine the insights we extract. Examples will be drawn from bulk stable isotopes from multiple elements (carbon, nitrogen, sulphur) and multiple tissues, and compound-specific stable isotopes of nitrogen. Examples will include discussion on the diet and trophic position of several species, notable the blacktip reef shark Carcharhinus melanopterus and the sicklefin lemon shark Negaprion acutidens, and several species of bony fishes.