The FoCal is a highly granular Si+W electromagnetic calorimeter combined with a conventional sampling hadronic calorimeter covering pseudorapidities of $3.4<\eta<5.8$, proposed to be installed in ALICE for data-taking in 2027--2029 at the LHC. The FoCal provides unique capabilities to measure small-$x$ gluon distributions via prompt photon production and will significantly enhance the scope of ALICE for inclusive and correlation measurements with mesons, photons, and jets to explore the dynamics of hadronic matter at small $x$ down to $\sim10^{-6}$.
In this seminar, I will try to give a complete overview of the physics potential, the technology choices and related R&D, and at the end will try to point out open areas of research.