The traditional partitioning of MIG welded joint is very coarse. The understanding regions of welded joint has evolved tremendously. A fusion weld joint was thought to consist of three regions, the fusion zone and HAZ, which is not sufficient. Examination of a welded joint reveals several distinct microstructure regions in this paper. The fusion zone and HAZ is subdivided. The previous technological probes allow one to compare the effects of base metal, welding conditions, welding consumables, constrains and give answers in the "better-worse".