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With the advent of new generation low-frequency telescopes, such as the LOwFrequency ARray (LOFAR), and improved calibration techniques, we have nowstarted to unveil the sub GHz radio sky with unprecedented depth andsensitivity. The LOFAR Two Meter Sky Survey (LoTSS) is an ongoing project inwhich the whole northern radio sky will be observed at 150 MHz with asensitivity better than 100 $\mu$Jy beam$^{-1}$ at a resolution of \asec{6}.Additionally, deeper observations are planned to cover smaller areas withhigher sensitivity. The Lockman Hole, the Bo\"otes and the Elais-N1 regions areamong the most well known northern extra-galactic fields, and the deepest ofthe LoTSS Deep Fields so far. We exploit these deep observations to derive thedeepest radio source counts at 150~MHz to date. Our counts are in broadagreement with those from the literature, and show the well known upturn at$\leq$ few mJy, mainly associated with the emergence of the star-forming galaxypopulation. More interestingly, our counts show for the first time a verypronounced drop around S$\sim$2 mJy, which results in a prominent `bump' atsub-mJy flux densities. Such a feature was not observed in previous counts'determinations (neither at 150 MHz nor at higher frequency). While samplevariance can play a role in explaining the observed discrepancies, we believethis is mostly the result of a careful analysis aimed at deblending confusedsources and removing spurious sources and artifacts from the radio catalogues.This `drop and bump' feature cannot be reproduced by any of the existingstate-of-the-art evolutionary models, and appears to be associated with adeficiency of AGN at intermediate redshift ($1<z<2$) and an excess oflow-redshift ($z<1$) galaxies and/or AGN.

Extremely deep 150 MHz source counts from the LoTSS Deep Fields