This lecture introduces the design of biochips and biosensors, emphasizing the need for probes and target biological molecules. It covers the motivation behind biochip development, showcasing real-world applications like the Quicklab project by Siemens and the FreeStyle Libre System. The lecture delves into the functions of the pancreas, the measurement of bio-markers, and the challenges in personalized therapy. It discusses the interface between CMOS circuits and bio-samples, the importance of bio-probes, and the applications of biochips in personalized therapy and animal monitoring. The lecture concludes by highlighting the design considerations for bio/CMOS interfaces and the future prospects of under-the-skin devices.