▁on ▁this ▁method , ▁referred ▁to ▁as ▁single ▁particle ▁analysis , ▁use ▁images ▁of ▁multiple ▁( ho pe fully ) ▁identical ▁objects ▁at ▁different ▁orient ations ▁to ▁produce ▁the ▁image ▁data ▁required ▁for ▁three - dimensional ▁reconst ruction . ▁If ▁the ▁objects ▁do ▁not ▁have ▁significant ▁preferred ▁orient ations , ▁this ▁method ▁does ▁not ▁suffer ▁from ▁the ▁missing ▁data ▁w edge ▁( or ▁cone ) ▁which ▁accomp any ▁tom ographic ▁methods ▁nor ▁does ▁it ▁in cur ▁excess ive ▁radiation ▁dos age , ▁however ▁it ▁assumes ▁that ▁the ▁different ▁objects ▁im aged ▁can ▁be ▁treated ▁as ▁if ▁the ▁ 3 D ▁data ▁generated ▁from ▁them ▁arose ▁from ▁a ▁single ▁stable ▁object . ▁ ▁Sample ▁prepar ation ▁ ▁Sample ▁prepar ation ▁in ▁T EM ▁can ▁be ▁a ▁complex ▁procedure . ▁ ▁T EM ▁spec im ens ▁should ▁be ▁less ▁than ▁ 1 0 0 ▁nan om eters ▁thick ▁for ▁a ▁conventional ▁T EM . ▁Un like ▁neut ron ▁or ▁X - R ay ▁radiation ▁the ▁electrons ▁in ▁the ▁beam ▁interact ▁readily ▁with ▁the ▁sample , ▁an ▁effect ▁that ▁increases ▁roughly ▁with ▁atomic ▁number ▁squ ared ▁( Z 2 ). ▁High ▁quality ▁samples ▁will ▁have ▁a ▁thick ness ▁that ▁is ▁compar able ▁to ▁the ▁mean ▁free ▁path ▁of ▁the ▁electrons ▁that ▁travel ▁through ▁the ▁samples , ▁which ▁may ▁be ▁only ▁a ▁few ▁tens ▁of ▁nan om eters . ▁Pre par ation ▁of ▁T EM ▁spec im ens ▁is ▁specific ▁to ▁the ▁material ▁under ▁analysis ▁and ▁the ▁type ▁of ▁information ▁to ▁be ▁obtained ▁from ▁the ▁spec imen