The method of taking isomers to a form of tautomers, or isomers of organic substances.
Huh?
OP, tautomerization is a chemical reaction that allows isomers of a chemical compound to interconvert. Isomers have the same number of atoms, just rearranged a bit. Most common example of tautomerization is the conversion of a ketone into an enol (see below). As you can see the first molecule has the same number of C's, O's and H's as the second molecule, but the arrangement of atoms is different.
The reaction is reversible. Most chemists imagine molecules (that can tautomerize) to exist as a mixture of tautomers, or even as a structure "in between" the two tautomers.
Hope this helps. BTW I presume you've looked up that famous online encyclopedia?
http://en.wikipedia.org/wiki/Tautomer