Dwarf galaxies are at the center of a long debated galaxy evolution puzzle. In the Local Group, there seems to be evidence that the exact morphology of a dwarf is strongly correlated with its environment: late-types (dwarf irregulars, dIrr) are further away from major group members than early-types (dwarf ellipticals and dwarf spheroidals, dE). In general, the early-types, with their smooth ellipsoid light distribution, have no detected interstellar medium (ISM), possess low angular momentum and have low current star formation rates. The late-types have an irregular appearance, large quantities of neutral hydrogen (HI), ongoing star formation and higher angular momentum.