Modern ultra-low power microcontrollers (i.e. TI MSP430) consume little energy making batteries unnecessary, even while sampling various sensors and communicating wirelessly. By properly managing low-power modes, scavenging energy from the environment enables infinite system uptime without the need for a battery. The various methods of energy harvesting will be discussed including vibration, solar and heat and the tips and tricks to enable an existing application to run from harvested energy.