Massive stars are those with more than ~8 solar masses, the limit above which stars may undergo a core collapse supernova (SN) explosion at the end of its life. They have played a critical role in how the Universe has evolved and to understand this role we need to know the physics ruling them and the evolutionary paths they follow. In the last decade, two impacting discoveries have shaken the field, the realization that ~70% of massive stars are in multiple systems that will interact during their lifetime, and the discovery of Black Hole+Black Hole and Black Hole+Neutron Star binaries via their gravitational waves. Thus the number of possible processes relevant for their evolution has multiplied. These processes include steady mass-loss during the early phases, as OB-type and B-Supergiant stars, episodic mass-loss at advanced phases such as Red Supergiants, magnetic fields, pulsation, mixing, convection, and mass and angular momentum transfer.

GLIMS (A GLobal vIew of Massive Stars) is a project that aims at achieving a new level in our understanding of the evolution of massive stars, going from understanding some stars under some conditions to understand all stars under all conditions. To reach that objective we imperatively need to increase our statistic of the different evolutionary paths. New surveys such as WEAVE-SCIP and A-SMASHER, together with Gaia data and the XSHootU collaboration will offer us the needed data. Appropriate heavy model computations and analysis tools are required to handle those data and obtain accurate and significant results. By combining the expertise of the Tenerife team in the early phases and that of the Alicante team at the youngest and oldest ages we will be able to face this challenge.