Crystals
Most of our samples are crystals with differing structures and patterns. Often times we put in diamond windows with miller indices. Prior to the beamtime they either characterize their crystal or send it to SSRL to do so.
X-Ray Diffraction
Bright spots
Dark spots 
This is how we take snap shots of our samples. These additions and subtractions of light give us spots on our detectors that tell us about the sample based. However, this can have issues because some bounce multiple times.
Energy band gaps
This give stuff their characteristic properties. Such as conduction, insulation, and semi conductor, and optical properties. The electrons closer to the bottom of the graph are deep in the atomic well and need tons of energy to wiggle or kick out. The ones at the top of the conduction band are easier to kick out and or wiggle with incoming light.
The energy band gap can move and change due to temperature. So we can manipulate the temp so we can take snap shots of the phase transistion.
