▁from ▁which ▁the ▁material ▁is ▁compr ised . ▁ ▁T issue ▁section ing ▁ ▁Bi ological ▁t issue ▁is ▁often ▁embedded ▁in ▁a ▁res in ▁block ▁then ▁th inned ▁to ▁less ▁than ▁ 1 0 0   nm ▁on ▁an ▁ul tr am icro t ome . ▁The ▁res in ▁block ▁is ▁f ract ured ▁as ▁it ▁passes ▁over ▁a ▁glass ▁or ▁diam ond ▁kn ife ▁edge . ▁This ▁method ▁is ▁used ▁to ▁obtain ▁thin , ▁minim ally ▁de formed ▁samples ▁that ▁allow ▁for ▁the ▁observation ▁of ▁t issue ▁ul tr astr ucture . ▁In organ ic ▁samples , ▁such ▁as ▁al umin ium , ▁may ▁also ▁be ▁embedded ▁in ▁res ins ▁and ▁ul tr ath in ▁section ed ▁in ▁this ▁way , ▁using ▁either ▁co ated ▁glass , ▁sa pp hire ▁or ▁larger ▁angle ▁diam ond ▁kn ives . ▁To ▁prevent ▁charge ▁build - up ▁at ▁the ▁sample ▁surface ▁when ▁view ing ▁in ▁the ▁T EM , ▁t issue ▁samples ▁need ▁to ▁be ▁co ated ▁with ▁a ▁thin ▁layer ▁of ▁conduct ing ▁material , ▁such ▁as ▁carbon . ▁ ▁Sample ▁st aining ▁ ▁T EM ▁samples ▁of ▁bi ological ▁t issues ▁need ▁high ▁atomic ▁number ▁st ains ▁to ▁enh ance ▁contrast . ▁The ▁st ain ▁absor bs ▁the ▁beam ▁electrons ▁or ▁sc at ters ▁part ▁of ▁the ▁electron ▁beam ▁which ▁otherwise ▁is ▁project ed ▁onto ▁the ▁imag ing ▁system . ▁Comp ounds ▁of ▁heavy ▁met als ▁such ▁as ▁os m ium , ▁lead , ▁u ran ium ▁or ▁gold ▁( in ▁imm