Francesco Ranzato's research work has been mostly focused on abstract interpretation, static analysis and verification of software systems. Abstract interpretation is a general methodology for designing and formally proving the correctness of approximations of computing systems. This technique provides generic and powerful tools for designing static program analyzers, automatic verifiers of software/hardware systems, type systems, security protocol analyzers, etc. Abstract interpretation is a lively research area: SAS and VMCAI are the flagship annual conferences devoted to research in abstract interpretation and static analysis, while a significant portion of accepted papers in top-tier programming languages conferences, like ACM PLDI and ACM POPL, concerns topics in abstract interpretation (the top 5 most cited articles at ACM POPL include three articles on abstract interpretation, in particular the most cited article). Abstract interpretation has a wide active community of European (in particular Italian, as witnessed by many Italian PRIN-funded research projects on abstract interpretation), American and Asian researchers. Abstract interpretation had (and still has) a great industrial impact. Noteworthy examples include: (1) the Polyspace static analyzer for C/C++ and Ada programs has been fully conceived and designed by abstract interpretation and is successfully commercialized by TheMathWorks; (2) Microsoft Visual Studio IDE incorporates an abstract interpretation-based static analyzer of .NET bytecode that allows to automatically derive correctness specifications, the so-called Code Contracts; (3) Astree is a C static analyzer based on abstract interpretation, conceived and designed by Patrick and Radhia Cousot's research group at ENS Paris, marketed by AbsInt GmbH (Germany), and used in the defense/aerospace (Airbus, Honda), electronic (Siemens), and automotive industries (Daimler). For the invention of abstract interpretation together with his wife Radhia Cousot (1947-2014), Patrick Cousot has been the recipient of: the French 1999 CNRS Silver Medal, a honorary doctorate from the Universit\"{a}t des Saarlandes (Germany), the 2013 ACM SIGPLAN Programming Languages Achievement Award, the 2014 IEEE Computer Society Harlan D. Mills Award and the 2018 IEEE John von Neumann Medal.