We present a low-cost, do-it-yourself system for complexmammalian cell culture under dynamically changing medium formulations by integrating conventional multi-well tissue culture plates with simple microfluidic control and system automation. We demonstrate the generation of complex concentration profiles, enabling the investigation of sophisticated input-response relations. We further apply our automated cell-culturing platform to the dynamic stimulation of two widely employed stem-cell-based in vitro models for early mammalian development: the conversion of naivemouse embryonic stemcells into epiblast-like cells andmouse 3Dgastruloids. Performing automatedmedium-switch experiments, we systematically investigate cell fate commitment along the developmental trajectory toward mouse epiblast fate and examine symmetry-breaking, germ layer formation, and cardiac differentiation in mouse 3D gastruloids as a function of time-varyingWnt pathway activation. With these proof-of-principle examples, we demonstrate a highly versatile and scalable tool that can be adapted to specific research questions, experimental demands, and model systems.