Cepheid variables are important astrophysical tool in time-domain astronomy, because its period-luminosity (PL) relation can be used to derive distance to nearby galaxies, and hence calibrating the Hubble constant via distance ladder. In this talk I will give an overview of some recent projects on Cepheids. The first one is the observation of Large Magellanic Cloud Cepheids in JHK bands, at which we derive the best LMC PL relation in these bands. The second project is the search of the ultra-long period Cepheids (ULPC) in M31 using the time-series PTF data. I will present the search results and analysis based on the follow-up observations of the ULPC candidates in M31, as well as their implication in distance scale work. The last project I will introduce is the calibration of the PL relation in 24-micron (ie. in mid-infrared) using a new sample of Galactic Cepheids.