A sharp view of the AGN central engine in M87

Due to its proximity and large black hole mass, the nearby radio galaxy M87 is a prime target for high-resolution imaging studies of an AGN central engine. In this talk, we will report on the first VLBI images of M87 obtained with the Global Millimeter VLBI Array in conjunction with the phased ALMA and the Greenland Telescope at a wavelength of 3.5 mm.