At my workplace, we are now completing the multiscale simulation of a full mouse brain (neuron/synaptic activity, cellular metabolism, etc). It fits into our small supercomputer first deployed in 2019, and there's a large potential for simplification not yet realized.

I believe that a supercomputer from the top 5 can already simulate a human brain. But we don't have the data and the theory yet. We are developing it, though.