Fundamental research on respiratory transport phenomena, quantifying momentum and mass transfer in the lung depths, is overwhelmingly focused on adults. Yet, children are not just miniature adults; their distinct lung structures and heterogeneous ventilation patterns set them aside from their parents. In RespMicroFlows, we will break this cycle and unravel the complex microflows characterizing alveolar airflows in the developing pulmonary acini. Our discoveries will foster ground-breaking transport strategies to tackle two urgent clinical needs that burden infants and young children. The first challenge relates to radically enhancing the delivery and deposition of therapeutics using inhalation aerosols; the second involves targeting liquid bolus installations in deep airways for surfactant replacement therapy.By developing advanced in silico numerical simulations together with microfluidic in vitro platforms mimicking the pulmonary acinar environment, our efforts will not only deliver a gateway to reliably assess the outcomes of inhaling aerosols and predict deposition patterns in young populations, we will furthermore unravel the fundamentals of liquid bolus transport to achieve optimal surfactant delivery strategies in premature neonates. By recreating cellular alveolar environments that capture underlying physiological functions, our advanced acinus-on-chips will deliver both at true scale and in real time the first robust and reliable in vitro screening platforms of exogenous therapeutic materials in the context of inhaled aerosols and surfactant-laden installations. Combining advanced engineering-driven flow visualization solutions with strong foundations in transport phenomena, fluid dynamics and respiratory physiology, RespMicroFlows will pave the way to a new and unprecedented level in our understanding and quantitative mapping of respiratory flow phenomena and act as catalyst for novel targeted pulmonary drug delivery strategies in young children.