Skeletal muscle's amazing malleability makes it the ultimate comparative tissue as it adapts to function in every possible environment over every possible time scale. Boutilier says `you can evolutionarily remove or add bits[from muscle] to give unique functions', resulting in the incredibly tight structure—function relationships that are described in this issue. He adds that skeletal muscle plays a unique role in evolution. It is ultimately the organ that determines how fast you can escape from a predator, or whether you catch your next meal. As such, it is the major tissue that determines whether your genes get through to the next round of selection.

Looking to the future, Hoppeler agrees with Johnston's closing observation,that `proteomics opens up the possibility of investigating all the proteins transcribed under particular environmental conditions and oligonucleotide array technology will allow coordinated gene expression to be studied,potentially at the whole-genome level.' Hoppeler adds that these modern techniques pave the way to understanding the molecular bases of skeletal muscle's interactions with other physiological systems. For example, he explains that `twenty years ago, we knew it was healthy to move around, but it wasn't clear why'. By repeatedly sampling an individuals' muscle and analysing the tissue at the molecular level, Hoppeler believes that we will begin to unravel muscle's role in the planets' declining health.

Ultimately, Hoppeler is very enthusiastic about muscles' `enormous potential for future research'. He describes muscle as the ideal model tissue for answering many of today's questions in both comparative and systems physiology, because `muscle comes in so many guises, there is something there for everyone!'