3D tissues that develop from a monolayer can take different forms: from folded monolayers -tubes or spheres - to bulk tridimensional tissues such as muscles, stratified epithelia, or epithelial tumors.  In vivo, muscle bilayers that surround large arteries or the intestine are oriented perpendicularly. This “crisscross” architecture, also observed in organisms like the hydra or in bulk tissues like the tongue, is the basis of so-called hydrostats that allow many degrees of freedom and are an inspiration in soft robotics.

In this talk, we will discuss the onset of formation of crisscross bilayers from a myoblast monolayer, and the particular role played by +1/2 topological defects in the orientation field of the initial monolayer. From these experiments and more recent ones conducted on mosaic microgrooved substrates presenting conflicts of orientations, we will show the importance of the microenvironment on the final architecture of the tissue. Finally, we will describe the formation of large cell mounds on substrates textured as integer “vortex” defects.