What is the most influential work of Grothendieck in mathematics?

Recently Alexander Grothendieck has passed away but his mathematical wave is still alive and passes its growth ages. It is hard to describe the influence of such a great man in mathematics just in few words and even more hard to determine a particular idea of him as the most influential but maybe some descriptive papers of some historians and expert researchers who work on his theories can help us to reach a better insight about it.

Question: What are examples of nice descriptive papers or books which are concentrated on impacts and connections of Grothendick's theorems and theories in mathematics, specially those which describe the influence of his works on those parts of mathematics which were developed before him and are under development now? In particular, as a logician I am interested in papers related to possible impacts of Grothendick's mathematical ideas on some fields of mathematicial logic like set theory and model theory.

Solution 1:

The correspondence between Grothendieck and Serre during the period 1955-1987 illustrates how Grothendieck's mathematical work shifted from functional analysis to algebraic geometry. The correspondence edited by the American Mathematical Society has the special flavour of being bilingual.

http://www.amazon.com/Grothendieck-Serre-Correspondence-Pierre-Colmez-Grothendieck/dp/B0088OUXXY/ref=sr_1_1?s=books&ie=UTF8&qid=1416203841&sr=1-1

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