Over the past decades, observations of the cosmic microwave background (CMB) have established the standard cosmological model, providing information to understand dark matter and dark energy. In the future, 21cm signals from neutral hydrogen have great potential for cosmological and astrophysical studies. In this talk, I will introduce the scientific goals of the current and future CMB observations and discuss the instrumentation and calibration of two ongoing CMB experiments: the Cosmology Large Angular Scale Surveyor (CLASS) and the Simons Observatory (SO). Then, I will discuss the 21cm signal as a powerful probe to study cosmic reionization and dark ages. I will introduce our novel mapping method and its advantage in recovering the 21cm power spectrum. With the CMB and 21cm observations, we will trace the entire history of the cosmological evolution, which will teach us about the early universe, dark matter, and dark energy..