After the illumination with 1700 W/cm 2 for 1 min, severe damage to the carbon films was seen, both in cryo-TEM and cryo-bright field microscopy (Fig. ). Further experiments were therefore conducted under vitreous conditions (< 55 W/cm 2 ) to prevent damage and devitrification of samples. We note that absorption of radiation in the vitrified buffer (mostly water) on the carbon film is wavelength-dependent (Fry & , so the damage from the laser can differ depending on the wavelength of illumination.