The photoacoustic effect is the generation of a sound wave upon absorption of a time-varying light beam. It has raised a lot of interest for biomedical applications, since it allows background-free absorption imaging of endogenous molecules (haemoglobin, melanin, lipids) or exogenous probes inside living organisms. One limitation of photoacoustic imaging is its depth-to-resolution ratio of around 200 (i.e. 1 µm resolution is only attainable at depth below 200 µm). Endoscopy provides a way to achieve high resolution imaging at larger depths. To avoid inflicting damage to the tissue upon insertion of an endoscopic probe, single multimode fibers (typical diameter of 125 µm) have been proposed as minimally invasive probes. However, when light propagates in a multimode fiber, it is projected into a large number of components (or modes) that undergo unpredictable phase delays, so that the output pattern is usually speckle-like and the spatial information is scrambled. In this workshop, we will show how to use wavefront shaping to compensate for mode scrambling and scan a focused laser spot at the output of a multimode fiber. Then we obtain a small cross-section endoscope that allows to acquire both photoacoustic and fluorescence images point-by-point. A Q-switched laser delivering nanosecond pulses at 532 nm is used to generate the photoacoustic signal. A digital-micromirror device (DMD) is used as a phase modulator for wavefront manipulation. The acoustic signal will be detected by a fiber-optic hydrophone, which measures the acoustic pressure optically using a Fabry-Pérot interferometer at the tip of the fiber. Images of absorbing patterns and red blood cells, as well as fluorescent beads, will be acquired.