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PSR J1023+0038 is a binary system that hosts a neutron star and a low-mass comma main sequence companion star. It has been observed to switch on timescales of years between a radio millisecond pulsar state and a disc-dominated state comma of uncertain origin. After its last switch to a disc-dominated state in 2013 comma the source has been the object of extensive multiwavelength monitoring campaigns comma during which the continuous switch between three X-ray modes (high comma low and flare) on timescales of 10 s has been observed. Here we propose the ultimate comma strictly simultaneous comma multi-wavelength campaign to study in detail this unique mode-switching phenomenon. We will involve NuSTAR comma XMM-EPIC comma Swift-UVOT comma XMM-OM comma VLT-HAWK-I comma and VLA observations to probe models using correlations and lags (a profitable tool to study the emission mechanisms) comma as well as establish differences among the power spectra of the multi-band light curves. We will also track the elusive pulsations along the spectral energy distribution.