Marvel not (mē thaumasēis). “Do not begin to wonder” (ingressive first aorist active subjunctive with mē), as clearly Nicodemus had done. In John the word thaumazō usually means “unintelligent wonder” (Bernard).
Ye must be born anew (dei humas gennēthēnai anōthen). Jesus repeats the point in Joh 3:3 (dei and the infinitive instead of ean mē and the subjunctive) with anōthen (from above) only and not ex hudatos.