Rav Tzadok was a child prodigy. He said about himself that when he was one year old, he would make a bracha on his mother's milk. At age two he davened from a siddur. By age three and a half he was learning Gemara with Tosfos. Before his Bar Mitzva he was already writing Shailos U'Tshuvos. He delivered four drashos at his Bar Mitzva which were printed in the Sefer Meishiv Tzedek. He was a rising star in the Litvishe world.
The turning point came after his first marriage came to a premature end, but his wife wouldn't accept a divorce. He wandered among the Gedolim to secure a Heter Mei'a to enable him to remarry. During this difficult period he met with the Shoel U'Maishiv (Rav Yosef Shaul Nathanson of Lublin), Rav Tzvi Hirsh Chayos, Rav Shlomo Kluger and others. He also met with great Chasidic Rebbes including Rav Shalom of Belz, the Divrei Chaim, the Chidushei HaRim, Rav Meir Premishaln and others. When he met Rav Mordechai Yosef Leiner, the Izhbetzer Rebbe and former talmid of the Kotzker Rebbe before breaking away, he found in him a soulmate. The Litvishe Rav Tzadok became his ardent Chasid. At the end, his first wife accepted the Get and he did not need a Heter Mei'a. He then remarried and moved to Lublin.
Under Rav Mordechai Yosef, Rav Tzadok learned together with another Litvak turned Chasid (and broke his father's heart in the process), Rav Leibele Eiger the grandson of Rebbi Akiva Eiger and son of Rav Shlomo Eiger. After the petira of Rav Mordechai Yosef in 1854, Rav Tzadok refused to take his mantle of his Rebbe and lead the Chassidim. Instead he pushed Rav Leibele Eiger to become the Rebbe. In the ensuing 33 years until Rav Leibele's petira he learned in solitude composing his multitude of seforim. In 1887 after Rav Leibele's petira, he again refused to lead the Chasidim and pushed for Rav Avrohom Eiger to lead the flock. This time however the Chasidim refused to give in and he ultimately became the Rebbe of Lublin.
He very much wanted to emigrate to Eretz Yisroel but his Chasidim would not hear of it. Rav Tzadok was Niftar on 9 Elul, 5660/1900. Although he did not leave behind any sons, he left the world with his vast writings which have made a profound impact on Jewish thinking moving forward. His seforim include, Pri Tzadik (Chumash), Divrei Sofrim, Otzar HaMelech (Rambam), Yisroel Kedoshim, Tzidkas HaTzadik, Taanas Hashovim, Kuntras Divrei Chalomos, and many others. Yehi Zichro Baruch.