Optical sectioning using 2PE autofluorescence. 2PE optical sectioning of Colpoda maupasi resting cysts, 21–32 μm average dimensions. Encystment is particularly widespread in species living in ephemeral fresh-water puddles and is induced by exhaustion of the food and drying out. The resulting images have been obtained at LAMBS-MicroScoBio exploiting autofluorescence primed using 740 nm excitation. A Chameleon-XR ultrafast Ti-Sapphire laser (Coherent Inc., USA) and a Nikon PCM2000 confocal scanning head have been used . Linear frame dimension is 70 μm, z steps have been performed every 0.5 μm, and not all the optical sections are imaged.