Master and Grandmaster and Challenger

Hey guys,

I just want to clarify a few things about the above mentioned tiers.

When a Diamond 1 player hits 100 LP, they enter the typical promos and if they succeed, they get Masters, but where does the LP start?

Also, when does the MMR system move you from Masters to Grandmasters, and then from Grandmasters to Challenger? I know challenger is something like top 200 players checked every day, but I don’t get grandmasters.

Thanks!