Thanks to my granddaughter’s insatiable curiosity, I now know that the chemical name of the protein titin contains 189,819 characters and takes an hour to pronounce.
If you want to see it spelled out, some poor soul spent a large portion of their lifespan typing it out here:
https://en.wiktionary.org/wiki/Appendix:List_of_protologisms/Long_words/Titin