The direct 3D visualization of large sections of biological tissues, made possible by multiphoton microscopy, has the potential to revolutionize our understanding of the relation between the structure and function of biological tissues, opening the way to impressive applications in biomedicine and drug delivery, in phytotherapy, and agricultural and food industries. In an ambitious multidisciplinary effort, Micro4Nano will develop new approaches and methods towards the 3D visualization of biological tissues, up to 1 mm in depth, combining hyperspectral imaging of autofluorescent species, with structural information from second-harmonic generation signals, functional information from multifunctional fluorescent labels and chemical information from Raman microscopy. A new generation of multifunctional nanocarriers for two-photon microscopy and drug delivery will be designed and extensively exploited towards real-time monitoring of living cells and tissues. In an intersectoral endeavour, microscopy will be combined with microfluidics to investigate the tissue behaviour under controlled perfusion conditions. Micro4Nano promotes international and multidisciplinary collaborations between experts in complementary fields, including microscopy, drug delivery, spectroscopy, chemical synthesis, theoretical and computational chemistry. The collaboration is implemented through 50 secondments (173 person month) of early-stage and experienced researchers, the organization of three network-wide events and a rich and coherent program of training activities. The network promotes an effective integrate training of researchers, boosting their career development, and promotes enhanced collaboration schemes between participant organizations. The direct involvement of industrial partners guarantees the timely exploitation of original results from advanced research laboratories towards innovative products and services.