Modular tissue engineering (TE) is based on the design, fabrication, and arrangement of replicated microtissue constructs

to generate functional tissues. The advantage of this strategy is to produce tissues that more closely mimic the complex

structure of native tissues/organs. High-precision technologies such as microfl uidics, 3D bioprinting, and electrospinning,

which support both cell- and scaff old-based biofabrication methods, are implemented in a bottom-up TE strategy. Bioreactors

are used in the last step of the tissue production process. Packed bed perfusion bioreactors are widely applied in bottom-up

tissue engineering due to their ability to control perfusion to tissues. Modeling and simulation software packages are used

as powerful tools to predict the perfusion and fl ow distribution to the tissues and to design robust bioreactors. This review

imparts on the recent advances in the fi eld of bottom-up TE process and provides comprehensive insights into the cell-based

and scaff old-based strategies used for the biofabrication/assembly of tissue building blocks (BBs). Microfl uidic devices and

3D-bioprinting technology are mentioned as precise controlling tools in this regard, the promoted applications of which are

swiftly growing.