The intense X-rays, courtesy of the Advanced Photon Source, let engineers see changes in the crystallike configuration of molecules that generate the rapid contraction in fly muscles. The X-resulting views have a resolution of 0.00006 sec, which let them see previously unsuspected interactions between various proteins as the muscles stretch and contract.
The researchers also had to build a "flight simulator" for flies. It tricks the fly into feeling as if it's flying free so it will generate a stable pattern of wing motions.