Our group investigates the emergent properties of collective cell behavior and its associations with developmental and reproductive biology. We have particularly studied the mechano-chemical interactions within mammalian tissues and seek to unravel the underlying design principles of multicellular system dynamics. Our approach combines fluorescence live-cell imaging with mathematical modeling to understand how chemical signaling is influenced by and regulates mechanical forces in multicellular tissues. In this seminar, I will present our findings on how extracellular signal-regulated kinase (ERK) activity mediates and generates mechanical forces within confluent epithelial monolayers, thereby governing the spatiotemporal patterns of cellular behavior and ERK signaling. I will also discuss preliminary results on how cell competition between healthy and DNA-damaged aberrant cells affects the emergence and disappearance of ERK patterns through the percolation of epithelial tissues. Then, I will shift focus to the collective dynamics of sperm within the epididymis of male reproductive tracts, as revealed through intravital imaging of mouse tissues. We will explore how collective sperm movement emerges from interactions with epididymal epithelial cells and its implications for mammalian reproductive success.