Biophysical Journal 86 5

Cover picture: Photo of a flash-cooled HEWL crystal (300 μm × 300 μm) soaked in fluorescein and mounted in a cryoloop at 100 K. Fluorescence is observed upon continuous laser illumination with blue light. Only the crystal, not the vitreous cryosolvent around it, contains fluorescein, which is at the origin of the green emitted light. See the article by Weik et al. on p. 3176.