are thus able to "walk" inside of everything to develop ubiquitous computing. In fact, in 2013, the computer size was reduced to 1 cubic millimeter (Figure 1a). [3] It was constructed by stacking dust-sized chips, including a central processing unit, a memory, a power management circuit, and a timer (Figure 1b) into a rectangular-shaped pile. End users can create a sensor system by adding an application layer, a temperature sensor for instance. A photovoltaic (PV) cell was placed in the top layer (layer 1) to harvest energy, and a microbattery was installed in layer 2 for energy storage. The size of the microbattery measured 1.1×1.69 mm 2 with a thickness of 150 µm. A computer with a similar structure and functionality but much smaller in size was developed in 2018 (Figure 1c). [4] The volume of only 0.04 mm 3 allows for a highly localized measurement of the cellular temperature, thus providing an accurate indicator of cellular metabolism. While these lab-level demonstrations show the future of ubiquitous computing, dustsized computers will only become a new class of computing platforms if they are available anywhere anytime, relying on energy-autonomous operation.The key challenge to realizing perpetual operation is the development of sub-millimeter-scale energy harvesters and storage devices. [2,5] Micro-thermoelectric generators convert heat into electricity, but their output power is too low to drive dust-sized chips. [6] Radiofrequency (RF) power converters suffer from low efficiency when reducing antenna sizes. PV Advances in microelectronics have enabled the use of miniaturized computers for autonomous intelligence at the size of a dust particle less than one square millimeter across and a few hundred micrometers thick, creating an environment for ubiquitous computing. However, the size mismatch between microbatteries and microelectronics has emerged as a fundamental barrier against the take-off of tiny intelligent systems requiring power anytime anywhere. Mainstream microbattery structures include stacked thin films on the chip or electrode pillars and on-chip interdigitated microelectrodes. Nevertheless, available technologies cannot shrink the footprint area of batteries while maintaining adequate energy storage. Alternatively, the on-chip self-assembly process known as micro-origami is capable of winding stacked thin films into Swiss-roll structures to reduce the footprint area, which exactly mimics the manufacture of the most successful full-sized batteries-cylinder batteries. In addition to discussing in detail the technical difficulties of reducing the size of on-chip microbatteries with various structures and potential solutions, this Perspective highlights the following two basic requirements for eventual integration in microcomputers: minimum energy density of 100 microwatt-hour per square centimeter and monolithic integration with other functional electric circuits on the chip.