Abstract: Microsystem devices have traditionally leveraged both wafer fabrication and packaging technologies born in the IC industry to implement sensing and actuation functions at microscopic scales. The inherent needs unique to microsystems motivated the development of the first products with wafer-level packages (WLPs) in the 1980’s. The development of products that utilized WLP technology continued into the 1990’s and on into the turn of the century due in large part to the needs of the automotive and later mobile electronics industries. The relentless drive to miniaturize and cost reduce electronic devices has caused the IC industry, in a reversal of the flow of technology, to look to the microsystems industry as a source of technology. Thus, in recent years, the IC industry has begun adopting on a wide scale, some of the WLP technologies that have been mature in the microsystem industry for many decades. These technologies include: through wafer vias, CMP, wafer bonding as well as multi-die assemblies and die stacking. This paper looks at the evolution of wafer-level packaging for microsystem products across many different markets and across the packaging hierarchy. While many technology demonstrations have been published prior to the devices highlighted in this paper, the emphasis in this paper is on WLP devices that have successfully navigated all of the possible pitfalls while traversing the challenging road to commercialization. Examples of WLP products that have been driven by market needs will be used to illustrate some of the advantages and challenges that are common to all successful wafer-level packages. The common threads found in these wafer-level packaged devices will provide insight into the technological challenges that will be encountered in the coming decades as microsystem technologies are used in ever increasingly diverse markets.