Light sheet microscopy, such as selective plane illumination microscopy (SPIM, ), is one of the most promising imaging tools in recent years. The three key advantages of SPIM are: minimal photo-toxicity by illumination of the sample selectively with a thin sheet of light, rapid camera-based image acquisition, and multi-view reconstruction. Since its introduction to the life sciences ten years ago, SPIM has found many applications ranging from 3D cell cultures to whole organism imaging. In particular model organisms like the fruit fly and the zebrafish have successfully been imaged and reconstructed during their development.
We have developed a whole suite of methods based on light sheet microscopy to tackle important questions of morphogenetic processes in zebrafish. A crucial element of our work has been the development of novel sample mounting techniques  for the long-term observation of fragile biological organisms [3, 4]. Lately, we have shown that three-dimensional (3D) volumes can be imaged almost instantaneously using electrically tunable lenses (ETL) in SPIM . This makes SPIM the fastest fluorescence microscopy technology for non-invasive 3D imaging. Even the dynamics of the beating zebrafish heart can be captured and the myo- and endocardial tissues as well as the blood can be visualized by 3D reconstruction . A major challenge in light sheet microscopy is the efficient processing of the image data that accumulates quickly in high-speed SPIM. It has become advisable to process the data in real time . I will give some examples of the unique capabilities of SPIM, especially for monitoring the development of the zebrafish heart  and the early endoderm .
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