The Vitrobot is an automatic freezing robot for cryogenic electron microscopy grid vitrification, enabling fast, reproducible freezing in hydrated form (vitrification) of grids for cryogenic electron microscopy observation. Preparation involves application of the sample to a grid, removal of excess liquid and rapid freezing by immersion of the sample (a thin layer of around 100 nm) in liquid ethane. Several parameters can be modified to optimize vitrification conditions for each sample: temperature, humidity, number of blots and different waiting and incubation times.