title: Microscopy tools for the investigation of intracellular lipid storage and dynamics.
abstract: BACKGROUND
  Excess storage of lipids in ectopic tissues, such as skeletal muscle, liver, and heart, seems to associate closely with metabolic abnormalities and cardiac disease. Intracellular lipid storage occurs in lipid droplets, which have gained attention as active organelles in cellular metabolism. Recent developments in high-resolution microscopy and microscopic spectroscopy have opened up new avenues to examine the physiology and biochemistry of intracellular lipids.
  
  
  METHODS
  The aim of this review is to give an overview of recent technical advances in microscopy, and its application for the visualization, identification, and quantification of intracellular lipids, with special focus to lipid droplets. In addition, we attempt to summarize the probes currently available for the visualization of lipids.
  
  
  CONCLUSIONS
  The continuous development of lipid probes in combination with the rapid development of microscopic techniques can provide new insights in the role and dynamics of intracellular lipids. Moreover, in situ identification of intracellular lipids is now possible and promises to add a new dimensionality to analysis of lipid biochemistry, and its relation to (patho)physiology.
authors.affiliation: Department of Human Movement Sciences and Human Biology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands. Electronic address: sabine.daemen@maastrichtuniversity.nl.
authors.forename: Sabine
authors.initials: S
authors.lastname: Daemen
authors.affiliation: Department of Genetics and Molecular Cell Biology, CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands; Institute for Molecular Cardiovascular Research (IMCAR), RWTH Aachen University, Aachen, Germany. Electronic address: mamj.vanzandvoort@maastrichtuniversity.nl.
authors.forename: Marc A M J
authors.initials: MAMJ
authors.lastname: van Zandvoort
authors.affiliation: Department of Molecular Spectroscopy, Max Planck Institute for Polymer Research, Mainz, Germany. Electronic address: parekh@mpip-mainz.mpg.de.
authors.forename: Sapun H
authors.initials: SH
authors.lastname: Parekh
authors.affiliation: Department of Human Movement Sciences and Human Biology, NUTRIM School for Nutrition and Translational Research in Metabolism, Maastricht University, Maastricht, The Netherlands. Electronic address: matthijs.hesselink@maastrichtuniversity.nl.
authors.forename: Matthijs K C
authors.initials: MKC
authors.lastname: Hesselink
keywords: BODIPY, Boron-dipyrromethene; CARS, coherent anti-stokes Raman scattering; CLEM, correlative light electron microscopy; CLSM, confocal laser scanning microscopy; DIC, differential interference microscopy; FA, fatty acid; FIB-SEM, focused ion beam scanning electron microscopy; FLIP, fluorescence loss in photobleaching; FRAP, fluorescent recovery after photobleaching; FRET, fluorescence resonance energy transfer; Fluorescent lipid probes; GFP, green fluorescent protein; HCV, hepatitis C virus; LD, lipid droplet; Lipid droplets; Live-cell imaging; Metabolic disease; NBD, nitro-benzoxadiazolyl; PALM, photoactivation localization microscopy; SBEM, serial block face scanning electron microscopy; SIMS, Secondary Ion Mass Spectrometry; SRS, Stimulated Raman Scattering; STED, stimulated emission depletion; STORM, stochastic optical reconstruction microscopy; Super-resolution; TAG, triacylglycerol; TEM, transmission electron microscopy; TOF-SIMS, time-of-flight SIMS; TPLSM, two-photon laser scanning microscopy; Vibrational microscopy