Cells are squishy and soft. Tiny nanometer-sized particles such as quantum sensors cannot move freely inside them due to viscous drag, which makes sensing challenging. Researchers at the Indian Institute of Science (IISc) have now developed a technique to precisely maneuver quantum sensors through these highly viscous biological environments, such as the interior of living cells, using magnetic microbots. This opens up possibilities for real-time, minimally invasive measurement of parameters like local viscosity and temperature inside cells.