It is shown that accurate structure refinements are possible from electron diffraction data obtained using areas 4-20 nm in diameter and 4-20 nm thick. To obtain accurate atomic positions it is essential to take the dynamic diffraction fully into account, for which new software was developed. Examples(La3Ni2B2N3, Ba2Ca3Cu5O10+δ and Ce5Cu19P12) are given of the structure refinements of known and unknown structures with R-values in the range 2-6%. The procedure reported in this paper opens the way to structure determination of particles in many materials of industrial and scientific interest which cannot be solved by conventional structure determination (e.g. because of small size, heavily twinned materials or small fractions in polyphase materials).