Ondrej Krivanek's early scientific research

- Ondrej Krivanek's early research at Cambridge and ASU.
- Channelling effects in EELS, EELS near edge structure, Ronchigrams.
- The projected charge-density approximation for cryo-EM.

In 1806, Humphrey Davey said that "nothing promotes the advancement of science so much as a new instrument". This paper reviews some of the lesser-known achievements of Ondrej's early career, and reminds us of the level of performance of instruments in those days, in order to appreciate how great has been the progress in instrumentation, much of it due to Ondrej and his leadership, since then. Some new results in the field of EELS are described, including extraction of the time-dependence of the dielectric response (with better time resolution than an X-ray free electron laser (XFEL)) from Nion EELS data. An approximation for atomic-resolution imaging which includes multiple scattering effects is given for biological samples, for use with aberration-corrected instruments when these become needed at the higher beam energies required to preserve the projection approximation, on which the 3D merging of single-particle cryo-EM images is based. We also discuss the requirements for out-running radiation damage using pulsed electron beams, a worthy final challenge for OLK.