We have investigated the fragmentation process of dense cores and star formation with ALMA in the prototypical low-mass star-forming region of the Taurus molecular cloud. The target samples were collected based on the precedented unbiased survey by single-dish telescopes. As a result of the ALMA ACA observations, we statistically derived the evolutional timescale of dense gas fragmentation as a few 10^4 yr. It tends to get smaller as the gas density increases, and our results demonstrate the cores with 10^6 cm^-3 density reach the free-fall time. This indicates dissipations of turbulence and/or magnetic fields that support the cores against gravitational collapse as they condense. Another remarkable result is the discovery of a hydrostatic first core candidate called as MC35. It is driving faint bipolar outflow despite the fact that no point-source is detected in any wavelength embedded in the prestellar core. It vitally requires follow-up higher-resolution observations to be confirmed. Even a core with an embedded protostar called MC27 (aka L1521F) exhibits substructures besides the protostellar core including an extended arc-like structure of ~ 1000 AU scale like a streamer. These imply that dense prestellar/protostellar cores have complex internal substructures and are highly dynamic. ALMA and high-resolution interferometric observations are powerful tools for studying the evolution of dense molecular gas even for prestellar cores.