  Switchbacks are rapid magnetic field reversals that last from seconds to
hours. Current Parker Solar Probe (PSP) observations pose many open questions
in regard to the nature of switchbacks. For example, are they stable as they
propagate through the inner heliosphere, and how are they formed? In this work,
we aim to investigate the structure and origin of switchbacks. In order to
study the stability of switchbacks, we suppose the small-scale current sheets
therein are generated by magnetic braiding, and they should work to stabilize
the switchbacks. With more than one thousand switchbacks identified with PSP
observations in seven encounters, we find many more current sheets inside than
outside switchbacks, indicating that these microstructures should work to
stabilize the S-shaped structures of switchbacks. Additionally, we study the
helium variations to trace the switchbacks to their origins. We find both
helium-rich and helium-poor populations in switchbacks, implying that the
switchbacks could originate from both closed and open magnetic field regions in
the Sun. Moreover, we observe that the alpha-proton differential speeds also
show complex variations as compared to the local Alfv\'en speed. The joint
distributions of both parameters show that low helium abundance together with
low differential speed is the dominant state in switchbacks. The presence of
small-scale current sheets in switchbacks along with the helium features are in
line with the hypothesis that switchbacks could originate from the Sun via
interchange reconnection process. However, other formation mechanisms are not
excluded.
