3D bioprinting from the micrometer to millimeter length scales: Size does matter

3D bioprinting has rapidly expanded from a niche technology and in to a versatile platform for fabricating tissues with complex geometries and features ranging from the cellular to organ length scales. Recent advances include the development of yield-stress support baths that enable soft hydrogels to be 3D printed in highly complex structures and vascular networks and successful implantation of 3D printed scaffolds in animal models and human patients towards regenerating bone, cartilage and muscle. However, the range of additive manufacturing technologies currently used each has distinct advantages and disadvantages, and specifically it is critical to understand how the resolution of these different approaches dictate structure and function of the engineered tissue constructs. This article offers a focused review on how the size of the biomaterial that is being deposited or polymerized, which can range over 4 orders-of-magnitude from ∼1 μm up to 1 mm, drives biological performance.