The outer parts of galaxies represent a new frontier in observational astronomy at the limits of faint surface brightness. We know little about these regions except that galaxies viewed deeply enough can usually be traced out to 10 stellar scale lengths or more, without any evident edge. We do not know in detail how the stars and gas got there and whether stars actually formed there or just scattered from the inner parts. Neither do we know as much as we'd like about the properties, elemental abundances, scale heights and kinematics of outer disk stars except for a limited view in the Milky Way (e.g., Bovy et al 2016) and the Andromeda galaxy (Dalcanton et al 2012). Yet the outer parts of disks are expected to be where galaxy growth is occurring today, and where the left-over and recycled cosmological gas accretes or gets stored for later conversion into stars in the inner disk (Lemonias et al 2011, Moffett et al 2012). The outer parts should also show the history of a galaxy's interactions with other galaxies, as the orbital time is relatively long. A high fraction of outer disks are lopsided too, correlating with the stellar mass fraction in the outer parts (i.e., the ratio of the stellar mass to the total from the rotation curve; Zaritsky et al 2013), perhaps because of uneven accretion, interactions, or halo sloshing (Ghosh et al 2016). This chapter reviews disk structure, star formation and stellar populations in the outer parts of nearby galaxies. General properties of these outer disks are in Sect. 2 to 7, and a focus on dwarf irregular galaxies (dIrrs) is in Sect. 8. The observational difficulties in observing the faint outer parts of disks are discussed in other chapters in this volume.