3D printing is a process of making physical objects from digital models layer by layer. This is typically achieved by depositing consecutive thin layers of material, and building the object from the bottom up.  In tissue engineering, 3D printing is quickly becoming a popular method for fabricating engineered tissues. Cells can be combined with hydrogels  to form "bio-inks" that can be used to print tissues with complex structures. One of the main advantages of 3D printing is that it can print with millimeter-level precision. It also can print using many different materials, creating structures that have various mechanical and chemical properties. 3D bioprinting is great for fabricating unique structures and at low cost, but there are still hurdles to be overcome. Firstly, is the translation of 3D printing technology towards biological applications. Traditional 3D printing processes usually operate under high temperatures or with UV light, both of which are harmful to cells. However, many methods have already been developed towards translating 3D-printing technology to cell-friendly applications, and more progress is being made every year. Additionally, 3D printing is difficult to scale up, as making a single construct can often take hours. Making one structure at a time is useful for prototyping, but may limit its utility in large-scale applications.