I deal with a lot of cryptographic documents (e.g. public keys) and https://lapo.it/asn1js/ is a godsend for making sense of them. You just paste in hex or pem, and it shows the full deconstructed format along with two-way 'syntax highlighting' where if you hover over part of the deconstruction it highlights the equivalent part of the binary data. Hit the 'load' button for a representative example.