We actually know very little about what's going on inside Uranus and Neptune, causing researchers to propose that these planets be called "rocky giants" instead.

Uranus and Neptune may not be 'ice giants' after all, new research suggests

Source: space
Source Link: https://www.space.com/astronomy/exoplanets/uranus-and-neptune-may-not-be-ice-giants-after-all-new-research-suggests