From the Sources
רַבִּי לֵוִי בְּשֵׁם רַבִּי יוֹחָנָן אָמַר אֲפִלּוּ אִסְטְרוֹבִּלִּין שֶׁל רֵחַיִּים נִמְחֶה. רַבִּי יְהוּדָה בַּר סִימוֹן בְּשֵׁם רַבִּי יוֹחָנָן אָמַר אֲפִלּוּ עֲפָרוֹ שֶׁל אָדָם הָרִאשׁוֹן נִמְחֶה. כַּד דָּרְשָׁה רַבִּי יְהוּדָה בְּצִפּוֹרִי בְּצִבּוּרָא וְלֹא קִבְּלוּ מִינֵיהּ. רַבִּי יוֹחָנָן בְּשֵׁם רַבִּי שִׁמְעוֹן בֶּן יְהוֹצָדָק אָמַר אֲפִלּוּ לוּז שֶׁל שִׁדְרָה, שֶׁמִּמֶּנוּ הַקָּדוֹשׁ בָּרוּךְ הוּא מֵצִיץ אֶת הָאָדָם לֶעָתִיד לָבוֹא, נִמְחָה. אַדְרִיָּאנוֹס שְׁחִיק עֲצָמוֹת שָׁאַל אֶת רַבִּי יְהוֹשֻׁעַ בֶּן חֲנַנְיָא אָמַר לוֹ מֵהֵיכָן הַקָּדוֹשׁ בָּרוּךְ הוּא מֵצִיץ אֶת הָאָדָם לֶעָתִיד לָבוֹא, אָמַר לוֹ מִלּוּז שֶׁל שִׁדְרָה, אָמַר לוֹ מִנַּיִן אַתָּה יוֹדֵעַ, אֲמַר לֵיהּ אַיְתִיתֵיהּ לְיָדִי וַאֲנָא מוֹדַע לָךְ, טָחֲנוֹ בָּרֵחַיִם וְלֹא נִטְחַן, שְׂרָפוֹ בָּאֵשׁ וְלֹא נִשְׂרַף, נְתָנוֹ בְּמַיִם וְלֹא נִמְחֶה, נְתָנוֹ עַל הַסַּדָּן וְהִתְחִיל מַכֶּה עָלָיו בְּפַטִּישׁ, נֶחְלַק הַסַּדָּן וְנִבְקַע הַפַּטִּישׁ וְלֹא חָסַר כְּלוּם. (Bereishit Rabba 28:3)
R. Levi said in the Name of R. Yochanan: Even the nether stone of a millstone was dissolved. R. Yehudah b. R. Simon said: Even the dust of Adam was dissolved. R. Yehudah said this, but the congregation would not accept it. R. Yochanan said in the name of R. Shimon b. Yehotzadak: even the luz of the spinal column, from which Hakadosh Baruch Hu, will cause man to blossom forth in the future, was dissolved.
Hadrian (may his bones rot) asked R. Yehoshua b. Chanania: ‘From what part will Hakadosh Baruch Hu causde man to blossom forth in the future?’ ‘From the luz of the spinal column,’ he replied. ‘How do you know that?’ he asked. ‘Bring me one and I will prove it to you,’ he replied. He threw in into the fire, yet it was not burnt; he put it in water, but it did not dissolve; he ground it between millstones, but it was not crushed; he placed it on an anvil and hit it with a hammer; the anvil broke and the hammer split, yet it remained intact. (Bereishit Rabba 28:3)
The Mabul was so destructive that every human being was pulverized into nothing. Even the luz bone did not survive. The luz bone is the bone at the base of the spine. Other opinions say that it is at the top of the spine, ie the base of the skull. My friend DD in the UK informs me that this is why people sometimes like to dab a little havdalah wine on their neck, – it is in order to strengthen the luz bone. It is the strongest bone in the human body. The midrash expains how it does not burn, and cannot be ground down. The luz bone is preserved after someone dies and in the future Hashem will use this bone to bring about Techiat HaMeitim, resurrection of the dead. The Generation of the Flood (dor HaMabul) were so wicked, however, that they will not be resurrected at techiat hameitim. There is only one meal that feeds the luz bone, it is the meal that is eaten after Shabbat goes out on Saturday Night, Malave Malka (Source: Mishna Berura 300:2)
We did a search on Sefaria.org and found this really cool source sheet about the luz bone: https://www.sefaria.org/sheets/50299
How to Eat it
This is a good week to make a big deal about Malave Malka in order to feed the luz bone. It is good really to do this every week. Set the table nicely, wash and eat bread. Eat a nice meal of something new that you did not eat at the three Shabbat Seudot.