Designing an efficient and functional bioartificial pancreas (BAP) at human scale to treat type I diabetes remains the Holy Grail in the 2010s, although investigations started in the 1970s. Biomimetic approaches need to be performed and evaluated to offer insulin secreting cells an environment close to the native pancreas, but also accounting for the interactions between the pancreas and other organs, and more specifically liver. This chapter outlines the concept, development and recent progress of BAP technology, with specific focus on interaction between BAP and the host environment. After the introduction of pancreas anatomy and physiology and the current treatments for diabetic patients, we will study how fulfill (or not) the requirements for an efficient BAP, regarding its different components: cell types, encapsulation methods, membranes and devices dedicated to several implantation sites. We conclude with a short discussion of future directions including BAP revascularization to improve the exchanges with the host and the impact of microtechnologies on the development of next generation of BAP.