MASSTART aims to provide a holistic transformation to the assembly and characterization of high speed photonic transceivers towards bringing the cost down to €1/Gb/s or even lower in mass production. This will guarantee European leadership in the Photonics industry for the next decade. MASSTART will surpass the cost metric threshold by using enhanced and scalable techniques: i) glass interface based laser/PIC and fiber/PIC coupling approaches, leveraging glass waveguide technology to obtain spot size and pitch converters in order to dramatically increase optical I/O density, while facilitating automated assembly processes, ii) 3D packaging (TSV) enabling backside connection of the high speed PIC to a Si carrier iii) a new generation of flip chip bonders with enhanced placement in a complete assembly line compatible with Industry 4.0 which will guarantee an x6 improvement in throughput and iv) wafer-level evaluation of assembled circuits with novel tools that will reduce the characterization time by a factor of 10, down to 1 minute per device. This process flow will be assessed with the fabrication and characterization of four different demonstrators, addressing the mid-term requirements of next generation transceivers required by Data Center operators and covering both inter- and intra- Data Center applications. These demonstrators are: i) a 4-channel PSM4 module in QSFP-DD format with 400G aggregate bit rate, ii) an 8-channel WDM module in a QSFP-DD format with 800G aggregate bit rate, iii) a 16-channel WDM on-board module delivering 1.6Tb/s aggregate line rate and iv) a tunable single-wavelength coherent transceiver with 600Gb/s capacity following the DP-64QAM modulation format on 64Gbaud/s line rate. Finally, MASSTART will interact closely with international bodies to ensure the compliance and standardization of the developed technology with other proposed packaging form factors for rapid commercialization.