These images show a few specialized immune cells, called dendritic cells (in green), sticking to and interacting with a bunch of tumor cells (red/purple), all of them embedded in a gel so they can move around and grow in 3D. These experiments showed that some dendritic cells (the ones visible here) stick to the tumor cells very well and can even squeeze between them. This is a behavior that is not understood or observed often by immunologists so it is exciting to see it outside of the body.