Foreword on the special issue of JSC on the occasion of MEGA 2017

This volume collects the papers presented in the occasion of the MEGA (Effective Methods in Algebraic Geometry) conference held in Nice (France) from June 12th to 16th, 2017. The volume was open to original research contributions presented in the Conference and also to further contributions. According to the MEGA tradition, Algebraic Geometry is interpreted broadly, including, among other topics, symbolic computations, commutative algebra, polynomial optimization, combinatorial techniques, tropical geometry and applications. The papers in this volume can be divided along the following themes Effective methods in commutative algebra, Hilbert functions, monomial ideals: papers 1-3; Projective Geometry and Singularities, Vector bundles on Projective Spaces: papers 4-6; Tropical Geometry, Combinatorics of Polyhedra and its use in Optimization problems: papers 7-10; Real solutions to polynomial equations: papers 11-12. We conclude this foreword with a very brief discussion of each of the papers.