▁pri ori ▁knowledge ▁are ▁on going . ▁ ▁Historical ▁development ▁▁ ▁The ▁first ▁pre cess ion ▁electron ▁diff raction ▁system ▁was ▁developed ▁by ▁Vincent ▁and ▁Mid g ley ▁in ▁Br istol , ▁UK ▁and ▁published ▁in ▁ 1 9 9 4 . ▁Pre lim inary ▁investigation ▁into ▁the ▁Er 2 Ge 2 O 7 ▁cry stal ▁structure ▁demonstrated ▁the ▁feas ibility ▁of ▁the ▁technique ▁at ▁reducing ▁dynam ical ▁effects ▁and ▁providing ▁quasi - kin emat ical ▁patterns ▁that ▁could ▁be ▁solved ▁through ▁direct ▁methods ▁to ▁determine ▁cry stal ▁structure . ▁ ▁Over ▁the ▁next ▁ten ▁years , ▁a ▁number ▁of ▁university ▁groups ▁developed ▁their ▁own ▁pre cess ion ▁systems ▁and ▁verified ▁the ▁technique ▁by ▁solving ▁complex ▁cry stal ▁structures , ▁including ▁the ▁groups ▁of ▁J . ▁G j onnes ▁( Os lo ), ▁M igli ori ▁( B olog na ), ▁and ▁L . ▁Mark s ▁( N orth western ). ▁▁ ▁In ▁ 2 0 0 4 , ▁N ano ME G AS ▁developed ▁the ▁first ▁commercial ▁process ion ▁system ▁capable ▁of ▁being ▁retro fit ▁to ▁any ▁modern ▁T EM . ▁This ▁hardware ▁solution ▁enabled ▁more ▁w ides p read ▁implementation ▁of ▁the ▁technique ▁and ▁sp ur red ▁its ▁more ▁main stream ▁ad option ▁into ▁the ▁cry stal log raph y ▁community . ▁Software ▁methods ▁have ▁also ▁been ▁developed ▁to ▁achieve ▁the ▁necessary ▁sc anning ▁and ▁desc anning ▁using ▁the ▁built - in ▁electron ics ▁of ▁the ▁T EM . ▁H RE M ▁Research ▁Inc ▁has ▁developed ▁the ▁Q ED ▁plug -