High-resolution in vivo time-lapse assays require repeated immobilization and imaging of whole animals. Here we report a high-throughput technology for screening Caenorhabditis elegans at cellular resolution over its entire lifespan inside standard multiwell plates using repeated immobilization, imaging and optical manipulation. our system does not use any fluidic or mechanical components, and can operate for tens of thousands of cycles without failure. It is also compatible with industrial high-throughput screening platforms and robotics, and it allows both chemical, and forward and reverse genetic screens. We used this technology to perform subcellular-resolution femtosecond laser microsurgery of single neurons in vivo, and to image the subsequent regeneration dynamics at subcellular resolution. our single-neuron in vivo timelapse analysis shows that neurite regrowth occurring over short time windows is significantly greater than that predicted by ensemble averaging over many animals. H igh-throughput screening (HTS) allows rapid identification of potential therapeutic targets and leads. Although high-throughput assays can be performed in vitro, thorough study of many biological phenomena, such as development, organogenesis, regeneration and aging, requires the use of animal models. The use of multicellular organisms also facilitates identification of off-target or toxic effects. The nematode Caenorhabditis elegans is one of the most commonly used multicellular organisms for HTS. As nematodes can be cultured and screened in liquid, many techniques currently used for screening cells can be adapted for C. elegans. The small size and simple physiology of C. elegans render it suitable for culture in 96-and 384-well plates in small volumes, and internal organs can be easily visualized because C. elegans is optically transparent. Investigation of C. elegans often involves high-content and time-lapse studies; however, these rapidly moving organisms must be immobilized to image cellular and subcellular processes. In addition, many physiological processes are stochastic and time-dependent (that is, development, aging), which requires multitime-point immobilization, tracking, and imaging of large numbers of individual animals.Commercially available technologies for HTS of C. elegans utilize flow cytometry [1][2][3] . Despite their speed, these systems can acquire only one-dimensional fluorescence images. Thus, assays requiring analysis of cellular and subcellular features are not feasible. In addition, optical measurements and manipulations, such as multiphoton 4 and confocal imaging, laser stimulation and laser microsurgery [5][6][7] , are not possible with such approaches. Recently, we and others developed microfluidic approaches for immobilization of C. elegans for high-throughput and highcontent screening. Mechanical immobilization (both active [8][9][10][11] and passive
12) and cooling 13 have been used to enable short-term immobilization. Three-dimensional multiphoton imaging 9,10 and femtosecond laser microsurger...