  Popular scientific summary -- The atmosphere of the Sun is envisioned as
composed of inherently complex, non-homogeneous, and dynamic layers. A detailed
understanding of the physical processes involved in these layers is still
lacking. For example, it is largely unknown why the outermost layer of the
Sun's atmosphere (the solar corona) is so much hotter than the photosphere by
millions of degrees. Astrophysicists think that the layer sandwiched between
the photosphere and the corona, known as the interface region, may hold the key
to a better understanding of the nature of this enigma. With the help of
coordinated high-resolution, ground- and space-based observations from the
Swedish 1-m Solar Telescope (SST) on La Palma, Spain, and NASA's Interface
Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory (SDO), along
with the support from an advanced numerical simulation, I aim to unlock some of
the mysteries surrounding the dynamics of the interface region with a focus on
small-scale jets, known as "spicules". Spicules are found almost everywhere on
the Sun's surface and at any given moment there can be as many as 10 million of
them rapidly shooting outwards. They are often found to be heated beyond
chromospheric temperatures and appear in the transition region and (even)
coronal passbands. Because of their "omnipresence", it is suggested that they
play a major role in energizing the outer atmospheric layers of the Sun. This
thesis focuses on the physical characteristics and dynamics of spicules, along
with their role in mass-balance and heating of the solar atmosphere.

Solar and Stellar Astrophysics