Abstract: The present invention relates to a method of preparing a sample of one or more molecule(s) for imaging with a cryo-electron microscope. The method comprises providing a carrier substrate, cryogenically cooling the carrier substrate to form a cryogenically-cooled carrier substrate, generating gas phase ions of the one or more molecule(s) by electrospray ionisation, decelerating the gas phase ions, receiving the gas phase ions on the cryogenically-cooled carrier substrate to form a sample for imaging with a cryo-electron microscope and shielding the cryogenically-cooled carrier substrate after the step of receiving the ions on the cryogenically-cooled carrier substrate. The step of decelerating the ions reduces the energy of each of the ions to be less than 20 eV per charge when received at the cryogenically-cooled carrier substrate. The present invention also relates to an apparatus for preparing a sample of one or more molecule(s) for a cryo-electron microscope.