 MEGARA (Multi-Espectrografo en GTC de Alta Resolucion para Astronomia) is an optical integral-field and multi-object spectrograph covering the visible light and near infrared wavelength range between 0.365 and 1 µm with a spectral resolution in the range R=6000-20000.The MEGARA IFU (also called the Large Compact Bundle, or LCB) offers a contiguous field of view of 12.5 arcsec x 11.3 arcsec, while the multiobject spectroscopy mode allows 92 objects to be observed simultaneously in a field of view of 3.5 arcmin x 3.5 arcmin by means of an equal number of robotic positioners.Both the LCB and MOS modes make use of 100 µm-core optical fibers (1267 in total) that are attached to a set of microlens arrays (with 623 spaxels in the case of the LCB and 92x7 in the case of the MOS) with each microlens covering an hexagonal region of 0.62 arcsec in diameter.