What assets can be securitized?

Could you elaborate on the range of assets that can potentially be securitized? Are we limited to traditional financial assets like loans and mortgages, or do modern innovations like digital currencies and non-fungible tokens (NFTs) also fall under this umbrella? Additionally, are there any specific criteria or requirements that an asset must meet in order to be considered suitable for securitization? It would be great to gain a deeper understanding of the types of assets that have been successfully securitized in the past and any potential future trends in this area.