A 3D-printed in vitro model biological microenvironment in examples discussed below may have one or more of the following features: (a) a gel matrix 3D-printed scaffold, wherein the gel matrix comprises a chemical composition configured to culture a first type of live cells, (b) a target chemical disposed at one or more locations within the gel matrix, the target chemical forming a chemical depot from which a chemical gradient is created within the gel matrix, (c) a conduit disposed within the gel matrix and defining a lumen comprising a second type of live cells, wherein the conduit is configured to enable at least some of the first type of live cells to migrate through the conduit and facilitate flow of at least: some of the live cells to an outlet of the conduit, or enable introduction of at least one of other cells, Achemical mediators, or drugs into the 3D-printed microenvironment.