Ambiq Micro is a University of Michigan spin-out that recently moved to Austin to develop its family of ultra-low power ARM-based microcontrollers. This talk will start with a look at the key ultra-low power circuits research that led to the founding of Ambiq Micro. In particular, I will start with a focus on the Phoenix Processor, an ultra-low voltage 8-bit microcontroller that consumes only 30 picowatts in sleep mode. I will then discuss the second-generation Phoenix Processor, which includes a solar cell, battery, and 32-bit ARM processor in a volume of only 9mm^3. The ultra-compact form-factor of this device makes it ideal for medical implantation, and the application of this device to intra-ocular pressure sensing will be discussed. Finally, I will discuss the family of ultra-low power ARM-based microcontrollers that Ambiq is currently developing for a wide range of ultra-mobile markets demanding unprecedented energy efficiency.