Effects of vascularization in the delivery of immune cells (THP‐1) to the tumor spheroids. A) Schematic of a vascularized tumor case in which the transport of immune cells is promoted through the capillary. B) Schematic of a nonvascularized tumor case in which the transport of immune cells is limited. C,D) When the THP1 cells were delivered to the tumor spheroid through the microvessels on the vascularized tumor chip, many of the THP1 cells were observed near the tumor spheroid (red: RFP‐HUVEC, green: GFP‐A549, and blue: THP1). E,F) When the THP1 cells were introduced through the main blood vessel, cells were barely observed near the tumor spheroids due to the limited cell transport. G,H) When the THP1 cells were treated on the blood vessel‐only chip, few cells were observed in the sprouted capillaries. Scale bar: 200 µm. I) Schematic of regions analyzed for immune cell transport. J) Cell number in each region in the cases of vascularized and nonvascularized tumors.