As per [Wikipedia](https://en.wikipedia.org/wiki/International_System_of_Units), the new definition of kilogram is, “The kilogram is defined by setting the [Planck constant](https://en.wikipedia.org/wiki/Planck_constant) *h* exactly to 6.62607015×10−34 J⋅s (J = kg⋅m2⋅s−2), given the definitions of the metre and the second.”, while that for Kelvin is, “The kelvin is defined by setting the fixed numerical value of the [Boltzmann constant](https://en.wikipedia.org/wiki/Boltzmann_constant) *k* to 1.380649×10−23 J⋅K−1, (J = kg⋅m2⋅s−2), given the definition of the kilogram, the metre, and the second.”
These are the only two, in the list of 7 which don’t help form an idea of what that quantity actually is.
In: Physics
Originally, the base SI units were defined using physical object. There was a reference kilogram for example. But as our understanding physics and ability to measure things developed, it was discovered that the reference objects were not the sizes we thought they were and that they would slowly change over time. Reference kilogram’s mass would unavoidably change over time. Instead, the units were redefined using fundamental constants, things that would never change. However, it is still useful to visualize the units using the old definitions outside of technical contexts. For example, a gram being the mass of cubic centimeter of liquid water is much easier to visualize and is closer enough to the real value that you can use it most of the time.
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