The vision of a world where pervasive integrated electronic systems are fully interconnected to collect, process, and exchange information leads to a significant growth trend in the global smart sensor market. However, powering Internet of Things (IoT) infrastructures of one trillion nodes with batteries poses considerable maintenance and management costs. In the framework of this increasing trend, this talk will highlight innovative circuital and systems-level strategies and techniques to drastically reduce power consumption and build battery-less and energy-autonomous electronic devices.The talk focuses on the low-cost and low-power consumption requirements for energy-efficient IC design. These demand a small area, low design effort, digital-like shrinkage across CMOS generations, and design/technology portability. Moreover, the possibility to exploit the digital (automated) design flow even for analog building blocks can dramatically reduce the design effort of any system-on-chip enabling aggressively supply-voltage scaled and/or regulator-less building blocks that can be powered directly from energy harvesters. As final remarks, the talk will show a system-level industrial overview, exploring the research progress in sustainable wireless sensor nodes that require minimal or no maintenance.