Every second year, an international graduate summer school is held on The Island of Ven in Sweden, organized between the Technical University of Denmark in Denmark and Tyndall National Institute in Ireland (www.biop.dk/biophotonics17/). At the school, 60 graduate students and postdocs from all over the world participate. When applying for admission into the school, students submit a three-page summary of their research, and they are selected on the basis of their summary. This call for papers reflects core topics of the school and highlights the fields optogenetics and label-free optical spectroscopy, respectively.

Cardiac Optogenetics
Optical targeting (stimulation or recording) allows distributed parallel access to thousands and even millions of cells and locations at the same time, and within the tissue setting; optical targeting is high-throughput by nature. To implement an "all-optical approach" to stimulate and record fast biological processes, such as neuronal or cardiac activity, one needs to inscribe light sensitivity to the underlying cells and tissues. This is done in a relatively straightforward way using optogenetic methods, i.e., genetically expressing fast-responding light-sensitive proteins from lower organisms into mammalian cells and tissues, including into human cells (patient-obtained stem-cell-derived cardiomyocytes or other cells). Combined with automated optical systems for stimulation and recording, this all-optical approach can yield a high-throughput platform for drug discovery, disease modeling, and cardiotoxicity testing. Implementation examples will be shown of such an automated platform. Furthermore, computer-aided feedback control and patterned light stimulation can facilitate the precise "wave steering" of electrical activity in live cardiac tissue for optical control of potentially lethal abnormalities, cardiac arrhythmias.

In-Vivo Label-Free Optical Spectroscopy
The application of spectroscopic technologies in medicine is a rapidly emerging and powerful approach for disease detection and therapy. Spectroscopic methods offer the great advantage of obtaining molecular information directly from the examined sample, e.g. cells or tissue, in a label-free manner to provide a clinician with adequate support in the form of clinically-relevant information under ex vivo and but also in vivo conditions. Within this contribution, we will particularly highlight recent advances in in-vivo optical spectroscopy for a differential disease diagnosis allowing for an accurate and early treatment. In this context, it has been demonstrated that the combination of different complementary spectroscopic techniques to a multimodal approach significantly increases the diagnostic reliability and holds great promise to achieve an in-vivo optical biopsy. We will start with discussing the basics of the most important spectroscopic techniques, like linear and nonlinear Raman and fluorescence technologies, diffuse optics, optical coherence tomography, photoacoustic imaging, etc., and their potential for in-vivo studies, e.g., their implementation as fiber probes to perform endospectroscopy. Overall, we will provide a summary on ongoing efforts in in-vivo multimodal optical spectroscopy for medical diagnosis and discuss the potential and limitations of these multimodal spectroscopic approaches to address existing unmet needs in intraoperative histopathology.

Contributed Papers
In addition to the above-mentioned topics, areas of interest for this special section include, but are not limited to:

• Photoacoustic tomography or microscopy, acousto-optical imaging
• Optical coherence tomography: light sources, systems, and applications
• Nonlinear microscopy, coherent Raman scattering microscopy, and high-resolution microscopy techniques
• Biomedical optical spectroscopy and imaging: systems and applications
• Tissue optics
• Optical trapping and manipulation, and their applications in biophotonics
• Lasers, supercontinuum lasers, fiber lasers and their biomedical applications.

All submissions will be peer reviewed. Peer review will commence immediately upon manuscript submission, with a goal of making a first decision within 6 weeks of manuscript submission. Special sections are opened online once a minimum of four papers have been accepted. Each paper is published as soon as the copyedited and typeset proofs are approved by the author. Submissions should follow the guidelines of JBO. Manuscripts should be submitted online at https://jbo.msubmit.net. A cover letter indicating that the submission is intended for this special section should be included.

This special section is planned as a collection of papers based on selected talks delivered at the 6th International Symposium Topical Problems of Biophotonics. The symposium is held biannually and consists of several conferences covering a broad range of topics within the biophotonics area. This year is a symposium milestone, celebrating the 10-year anniversary of the event. The symposium is organized as a multidisciplinary platform aimed at bringing together physicists, biologists, and medical doctors. Modern optical technologies provide wide possibilities for both complex multiscale diagnostics and treatment of various pathologies and diseases. The aim of the special section is to give an overview of the state-of-the-art development in optical biomedical imaging and treatment techniques and their translation to clinical practice. This special section will cover a wide range of problems in biophotonics varying from fundamental aspects of light propagation in tissues and light-tissue interaction through principles of image formation, enhancement, and processing, to particular applications of optical techniques and devices in the laboratory and clinical environment.

Specific topics include, but are not limited to:

• Biomedical spectroscopy and microscopy
• Coherence domain optical methods and optical coherence tomography Optoacoustics
• Optical diffuse tomography and spectroscopy
• Fluorescence imaging
• Laser-tissue interaction
• Novel approaches in photodynamic therapy
• Optical techniques in translational medicine

All submissions will be peer reviewed. Peer review will commence immediately upon manuscript submission, with a goal of making a first decision within 6 weeks of manuscript submission. Special sections are opened online once a minimum of four papers have been accepted. Each paper is published as soon as the copyedited and typeset proofs are approved by the author. Submissions should follow the guidelines of JBO. Manuscripts should be submitted online at https://jbo.msubmit.net. A cover letter indicating that the submission is intended for this special section should be included.