A magnetic resonance device for monitoring growth of tissue in one or more bioreactors. The device can include a first magnet and a second magnet that can form a uniform magnetic field of desired strength around at least one sample of effluent from at least one bioreactor. At the command of a controller, an RF signal can illuminate the at least one magnetized sample, and sensors can detect at least one echo signal from the at least one magnetized sample. The controller can characterize the at least one sample based on the at least one echo signal. A resonator can shape the at least one echo signal.