IGFBP1 and neoplasm: Accumulating evidence show that a variety of physical force stimuli will give rise to reactive oxygen species (ROS),[17] which is unevenly distributed in the cells.[18] Excessive ROS causes cell apoptosis.[19] To determine whether IGFBP1 promotes the survival of confined cells by scavenging excessive ROS, we measure the level of ROS in spatially‐confined tumor cells with or without IGFBP1 depletion by using the genetically‐encoded fluorescent biosensors, mitochondria‐targeted redox sensing GFP (mito‐roGFP) and cytosol‐targeted redox sensing GFP (cyto‐roGFP).