  The sixth generation (6G) communication networks are featured by integrated
sensing and communications (ISAC), revolutionizing base stations (BSs) and
terminals. Additionally, in the unfolding 6G landscape, a pivotal physical
layer technology, the Extremely Large-Scale Antenna Array (ELAA), assumes
center stage. With its expansive coverage of the near-field region, ELAA's
electromagnetic (EM) waves manifest captivating spherical wave properties.
Embracing these distinctive features, communication and sensing capabilities
scale unprecedented heights. Therefore, we systematically explore the
prodigious potential of near-field ISAC technology. In particular, the
fundamental principles of near-field are presented to unearth its benefits in
both communication and sensing. Then, we delve into the technologies
underpinning near-field communication and sensing, unraveling possibilities
discussed in recent works. We then investigated the advantages of near-field
ISAC through rigorous case simulations, showcasing the benefits of near-field
ISAC and reinforcing its stature as a transformative paradigm. As we conclude,
we confront the open frontiers and chart the future directions for near-field
ISAC.
