Eurorack is already pretty small as a format, however 2HP take the concept of small format modular and really go to town with it.
HP is the width of measurement used for the eurorack format and 2hp is really the smallest width you could ever hope to fit anything functional in.
2hp specifically make modules in 2hp.
More info at 2hp
Virtual knobs and jacks controlling over 160 virtual modules
Part 2 on revisions that made synths into brand new machines