The behavior and microscale processes associated with freely suspended organisms, along with sinking particles underlie key ecological processes in the ocean. Mechanistically studying such multiscale processes in the laboratory presents a considerable challenge for microscopy: how to measure single cells at microscale resolution, while allowing them to freely move hundreds of meters in the vertical direction? Here we present a solution in the form of a scale-free, vertical tracking microscope, based on a ‘hydrodynamic treadmill’ with no bounds for motion along the axis of gravity. Using this method to bridge spatial scales, we assembled a multiscale behavioral dataset of nonadherent planktonic cells and organisms. Furthermore, we demonstrate a ‘virtual-reality system for single cells’, wherein cell behavior directly controls its ambient environmental parameters, enabling quantitative behavioral assays. Our method and results exemplify a new paradigm of multiscale measurement, wherein one can observe and probe macroscale and ecologically relevant phenomena at microscale resolution. Beyond the marine context, we foresee that our method will allow biological measurements of cells and organisms in a suspended state by freeing them from the confines of the coverslip.

与自由悬浮生物相关的行为和微观过程以及下沉颗粒是海洋中关键生态过程的基础。在实验室中机械地研究这种多尺度过程给显微镜带来了相当大的挑战：如何以微尺度分辨率测量单个细胞，同时允许它们在垂直方向上自由移动数百米？在这里，我们以无标度垂直跟踪显微镜的形式提出了一种解决方案，该解决方案基于“流体动力跑步机”，沿重心轴的运动不受限制。使用这种方法来连接空间尺度，我们组装了非粘附浮游细胞和生物的多尺度行为数据集。此外，我们展示了一个“单细胞虚拟现实系统”，其中细胞行为直接控制其周围环境参数，从而实现定量行为分析。我们的方法和结果体现了一种新的多尺度测量范式，其中人们可以在微尺度分辨率下观察和探测宏观尺度和生态相关现象。在海洋环境之外，我们预计我们的方法将允许通过将细胞和生物体从盖玻片的限制中解放出来，对处于悬浮状态的细胞和生物体进行生物测量。