▁al . ▁described ▁the ▁direct ▁visual ization ▁of ▁light ▁atoms ▁such ▁as ▁carbon ▁and ▁even ▁hydro gen ▁using ▁T EM ▁and ▁a ▁clean ▁single - layer ▁graph ene ▁substr ate . ▁ ▁Background ▁ ▁Elect rons ▁The oret ically , ▁the ▁maximum ▁resolution , ▁d , ▁that ▁one ▁can ▁obtain ▁with ▁a ▁light ▁mic ros cope ▁has ▁been ▁limited ▁by ▁the ▁w avel ength ▁of ▁the ▁phot ons ▁that ▁are ▁being ▁used ▁to ▁pro be ▁the ▁sample , ▁ λ , ▁and ▁the ▁numerical ▁a pert ure ▁of ▁the ▁system , ▁NA . ▁ ▁where ▁n ▁is ▁the ▁index ▁of ▁ref raction ▁of ▁the ▁medium ▁in ▁which ▁the ▁l ens ▁is ▁working ▁and ▁α ▁is ▁the ▁maximum ▁half - angle ▁of ▁the ▁cone ▁of ▁light ▁that ▁can ▁enter ▁the ▁l ens ▁( see ▁numerical ▁a pert ure ). ▁Early ▁tw enti eth ▁century ▁scient ists ▁the or ized ▁ways ▁of ▁getting ▁around ▁the ▁limitations ▁of ▁the ▁relatively ▁large ▁w avel ength ▁of ▁visible ▁light ▁( w avel ength s ▁of ▁ 4 0 0 – 7 0 0 ▁nan om eters ) ▁by ▁using ▁electrons . ▁Like ▁all ▁matter , ▁electrons ▁have ▁both ▁wave ▁and ▁particle ▁properties ▁( as ▁the or ized ▁by ▁Louis - V ict or ▁de ▁Bro g lie ), ▁and ▁their ▁wave - like ▁properties ▁mean ▁that ▁a ▁beam ▁of ▁electrons ▁can ▁be ▁focused ▁and ▁diff ract ed ▁much ▁like ▁light ▁can . ▁The ▁w avel ength ▁of ▁electrons ▁is ▁related ▁to ▁their ▁kin etic ▁energy ▁via ▁the ▁de