Among the many typical biological structures, cylindrical and tubular structures such as hyphae, stems, roots, blood vessels, airways, oesophagus, and tree trunks abound in nature. Tubes are typically used for transport, mechanical support or both. Their morphogenesis usually involves complex genetic and biochemical processes mediated by mechanical forces. In many cases, tubes have (at least) two layers glued together. Each layer has different mechanical and geometric properties. Moreover, due to growth taking place in the layers, each tube may also develops residual stresses. In this talk, I will be discussing the range of mechanical properties and functions that can be obtained by tuning these different properties within the framework of nonlinear morphoelasticity. In particular, I will discuss how differential axial growth can be used to improved structural stiffness (with examples from plants and arteries), how relative radial growth of the tube can either induce hollowing (as found in plant aerenchyma), or generate mucosal folding (as found in oesophagus and airways), and how anisotropy can induce handedness reversal (as found in phycomyces). Given time, I will also discuss the inverse problem of designing a tube with desired mechanical properties through growth and remodelling.