Microscopic singularity
From Memory Alpha, the free Star Trek reference
A microscopic singularity (or microsingularity) is a naturally occurring phenomenon that can be described as a tiny black hole.
Prior to 2151, Vulcan scientists theorized the existence of microsingularities, but their Human colleagues dismissed them as a "Vulcan myth" due to the lack of hard evidence.
In 2151, the Enterprise NX-01 rendezvoused with a Tesnian ship at an asteroid field, during which a microsingularity collided with the Tesnian ship and caused it to crash. Three microsingularities also struck the Enterprise, dissipating on impact when they encountered its polarized hull plating. Shortly after, Shuttlepod 1 was also struck by a microsingularity, which passed directly through its hull and threatened on-board life support. (ENT: "Shuttlepod One")
In early 2371, a microscopic singularity passed through the Sol system. When the singularity exploded, its energy interacted with the chroniton particles embedded in the ablative armor of the USS Defiant, which at the time was in orbit around Earth. The energy thus shifted the particles into a high state of temporal polarization.
With the Defiant's crew unaware of this event, Commander Benjamin Sisko, Lieutenant Jadzia Dax, and Doctor Julian Bashir transported down to Earth to address the Annual Starfleet Symposium in San Francisco. However, in passing through the temporally polarized chronitons, the transporter beam was redirected through time, and the three Starfleet officers ended up in San Francisco of 2024. (DS9: "Past Tense, Part I")
