Advanced systems based on bioreactors and scaffolds are an essential step towards the development of more predictive and ethical alternatives to animal experiments. Size, modularity, automation, monitoring and essential design are crucial because these elements will ease the transition from old technology and accelerate their acceptance into mainstream research. Based on these requirements, the interconnected transparent sensorised â€œlegoâ€ bioreactors designed in our labs have been used to generate physiologically relevant disease and toxicity models which recapitulate systemic responses impossible to observe in standard cell cultures. The disease model is an interconnected bioreactor circuit with i) adipose tissue in 3D in 3 different concentrations representing normo-weight, over weight and obese body mass indices, ii) human hepatocytes on porous collagen scaffolds and iii) monolayers of human endothelial cells. High adiposity and elevated glucose levels induce systemic and endothelial inflammation in the circuit, as observed in overweight and diabetic humans (Iori et al., 2012). Using similar technology a three-tissue circuit for monitoring the absorption, distribution, metabolism and toxicity of nanoparticles was developed in the context of the EU project InLiveTox (Ucciferri et al., 2014). The results were strikingly similar to those observed in animal experiments demonstrating that the dynamic 3D in-vitro models are ethical, meaningful and economically viable replacements.