The heart-on-a-chip is a 3D Cardiac Strip assay cultured in a 384-well screening format. We have successfully miniaturized the 3D cardiac strip to less than 5.000 hiPSC-cardiomyocytes per strip (compare: current standard 500k – 1M hiPSCs/strip), and we are able to reliably measure force of contraction, relaxation and contractile kinetics in this miniaturized setting.