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Classical Cepheids (hereafter Cepheids) belong to a class of important variable stars that can be used to determine distances to nearby galaxies via the famous period-luminosity (PL) relations, i.e. the Leavitt Law. In turn, these distances can then be used to calibrate a host of secondary distance indicators located well within the Hubble ow, and ultimately determine the Hubble constant in a manner independent of the Cosmic Microwave Background (CMB) measurements. Some recent progress in determining the Hubble constant to within 3% level via the Cepheid-based distance scale ladder (the SH0ES and the Carnegie Hubble Program) were rst summarized in this Proceeding, followed by a brief discussion on the prospect of using ultra-long period Cepheids (ULPC) in future distance scale work. ULPC are those Cepheids with periods longer than 80 days, which seem to follow a dierent PL relation than their shorter period Cepheids. It has been suggested that ULPC can be used to determine the Hubble constant in "one-step". However, based on the two ULPCs found in M31, it was found that the large dispersion in derived distance moduli leads to a less accurate distance modulus to M31 compared to the classical Cepheids. This nding might raise an alert regarding the use of ULPCs in future distance scale work.

APPLICATION OF CEPHEIDS TO DISTANCE SCALE: EXTENDING TO ULTRA-LONG PERIOD CEPHEIDS