A new microfluidic device takes a step toward mimicking human metabolism for applications such as drug testing. Hanry Yu of the Institute of Bioengineering & Nanotechnology and the National University of Singapore and coworkers have developed a three-dimensional microfluidic cell culture system with compartments containing lung, liver, kidney, and adipose cells (Lab Chip, DOI: 10.1039/b915147h). The compartments are spatially isolated but fluidically linked. Each compartment consists of a central section where cells are immobilized on a micropillar array and two flanking channels through which the medium flows and diffuses into the cells. During cell culture, the medium flows through the lung compartment first and then through the other three compartments in parallel. The researchers optimized a single culture medium to use with all four cell types. They found that adding growth factors enhanced lung cell function but inhibited liver cell function, so they encapsulated the growth factor in controlled-release gelatin microspheres. Adding the microspheres to the culture medium improved lung cell function without hurting the other cells.