  We present a summary of our recent work on the vertical distribution of the
resolved stellar populations in six low mass, edge-on, spiral galaxies observed
with the Hubble Space Telescope Advanced Camera for Surveys (HST/ACS). In each
galaxy we find evidence for an extraplanar stellar component extending up to 15
scale heights (~3.5 kpc) above the plane. We analyze the vertical distribution
as a function of stellar age by tracking changes in the color-magnitude
diagram. The young stellar component (< 10^8 yrs) is found to have a scale
height larger than the young component in the Milky Way, suggesting that stars
in these low mass galaxies form in a thicker disk. We also find that the scale
height of a stellar population increases with age, with young main sequence
stars, intermediate age asymptotic giant branch stars, and old red giant branch
stars having succesively larger scale heights in each galaxy. The color
distributions of the red giant branch (RGB) stars well above the midplane
indicate that the extended stellar components we see are moderately metal-poor,
with peak metallicities of [Fe/H] ~ -1 and with little or no metallicity
gradient with height. The lack of metallicity gradient can be explained if a
majority of extraplanar RGB stars were formed at early times and are not
dominated by a younger heated population. Our observations suggest that, like
the Milky Way, low mass disk galaxies also have multiple stellar components. We
examine our results in light of disk heating and merger scenarios and conclude
that both mechanisms likely played a role in forming the disks of our sample
galaxies.
