▁processes ▁down ▁to ▁tens ▁of ▁nan ose cond s ▁and ▁tens ▁of ▁nan om eters . ▁ ▁Lim itations ▁There ▁are ▁a ▁number ▁of ▁draw back s ▁to ▁the ▁T EM ▁technique . ▁Many ▁materials ▁require ▁extensive ▁sample ▁prepar ation ▁to ▁produce ▁a ▁sample ▁thin ▁enough ▁to ▁be ▁electron ▁transparent , ▁which ▁makes ▁T EM ▁analysis ▁a ▁relatively ▁time - consum ing ▁process ▁with ▁a ▁low ▁through put ▁of ▁samples . ▁The ▁structure ▁of ▁the ▁sample ▁may ▁also ▁be ▁changed ▁during ▁the ▁prepar ation ▁process . ▁Also ▁the ▁field ▁of ▁view ▁is ▁relatively ▁small , ▁raising ▁the ▁possibility ▁that ▁the ▁region ▁analyz ed ▁may ▁not ▁be ▁characteristic ▁of ▁the ▁whole ▁sample . ▁There ▁is ▁potential ▁that ▁the ▁sample ▁may ▁be ▁dam aged ▁by ▁the ▁electron ▁beam , ▁particularly ▁in ▁the ▁case ▁of ▁bi ological ▁materials . ▁ ▁Resol ution ▁limits ▁ ▁The ▁limit ▁of ▁resolution ▁obtain able ▁in ▁a ▁T EM ▁may ▁be ▁described ▁in ▁several ▁ways , ▁and ▁is ▁typically ▁referred ▁to ▁as ▁the ▁information ▁limit ▁of ▁the ▁mic ros cope . ▁One ▁commonly ▁used ▁value ▁is ▁a ▁cut - off ▁value ▁of ▁the ▁contrast ▁transfer ▁function , ▁a ▁function ▁that ▁is ▁usually ▁quoted ▁in ▁the ▁frequency ▁domain ▁to ▁define ▁the ▁reprodu ction ▁of ▁spatial ▁frequencies ▁of ▁objects ▁in ▁the ▁object ▁plane ▁by ▁the ▁mic ros cope ▁opt ics . ▁A ▁cut - off ▁frequency , ▁q max , ▁for ▁the ▁transfer ▁function ▁may ▁be ▁approxim ated ▁with ▁the ▁following ▁equation , ▁where ▁Cs ▁is ▁the ▁spher ical ▁aber r ation ▁coefficient