This project developed a low-power energy harvesting system that is capable of measuring and storing precise temperature data over long periods of time. Notably, this project was designed to avoid the use of a battery and is able to last a minimum of 30 days without losing functionality. Power for the system is harvested from surrounding energy sources, which in our case is indoor lighting. The most critical and challenging part of this system is the power-management circuitry, which is responsible for regulating power to the rest of the system. This circuitry uses clever combinations of MOSFETs, integrated circuits, and passive components to accomplish this goal. Other critical portions of the system are the MCU, which collects and records the temperature data, and the programming interface. Future developments should include the expansion to work with other energy sources such as thermal or piezoelectric, as well as a lower-power data storage system, as the current system is power-expensive.