SelectBIO Fifth Annual Organ-on-a-Chip World Congress 2019 focuses on an important and expanding field wherein cells are being assembled using Microfluidics and Lab-on-a-Chip technologies in a functionally-relevant manner. These clusters of "assembled cells" have functional significance and can mimic in vivo organ structure. Liver cells assembled on-board chips in a physiologically-relevant architecture using microfluidics can, for instance, be utilized for toxicity screening and the ability to assemble organ fragments ex vivo can provide an exquisite means to reconstruct biological processes (both physiological and pathological) "in a dish" or "on a chip." A number of chips such Lung-on-a-Chip, Brain-on-a-Chip, Gut-on-a-Chip, Marrow-on-a-Chip, Bone-on-a-Chip, Nerve-on-a-Chip amongst others have been built and will be presented and explored at this conference. We will also focus on "disease-on-a-chip", cancer-on-a-chip, immune system-on-a-chip.