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In a recent event in my institution, Leica representative mentioned  
that visible (70 nm resolution) and TREX STED (25 nm resolution) are  
feasible. I as far as I can remenber the problem with these techniques  
is the power of the laser required to deplete the fluorophore  
emission. It requires very powerful pulsed lasers and there is no  
commercially available visible laser with enough power to do this. And  
the prototypes are very expensive.

I searched the web and found papers describing TREX-STED. I won't  
comment on the numbers of laser power they give because that is beyond  
my competence, but perhaps someone here with more expertise could look  
at this numbers and enlighten rest of us.

Lenaldo Rocha