  The on-demand tailoring of light's spatial shape is of great relevance in a
wide variety of research areas. Computer-controlled devices, such as Spatial
Light Modulators (SLMs) or Digital Micromirror Devices (DMDs), offer a very
accurate, flexible and fast holographic means to this end. Remarkably, digital
holography affords the simultaneous generation of multiple beams
(multiplexing), a tool with numerous applications in many fields. Here, we
provide a self-contained tutorial on light beam multiplexing. Through the use
of several examples, the readers will be guided step by step in the process of
light beam shaping and multiplexing. Additionally, on the multiplexing
capabilities of SLMs to provide a quantitative analysis on the maximum number
of beams that can be multiplexed on a single SLM, showing approximately 200
modes on a single hologram.
