
i dont understanndd, the embryo part pls explainn

Loooong comment ahead.
Brief explanation of the invitrofertilization part of this webtoon.
Embryos are the suuuuper early stages of a fetus. Like a combination of egg and sperm. Not yet baby.
Depositing an embryo means combining the egg and sperm in a laboratory and freezing it for later use until the couple is ready or when the parent/s finds a surrogate. Etc.
Yiyi took his sperm to the lab, deposited an embryo together with an egg from some other donor and expected to have his biological son. (This process btw requires tons of money )
But our Fengfeng made the lab replace Yiyu's sperm with his. Thus poof it became Rourou. Feng's biological son. At least he wasn't as evil enough to throw Yiyi's sperm. He let the lab freeze Yiyi's sperm. Just like depositing an embryo, a sperm and an egg can also be frozen and stored if you still aren't ready, but worrying if you won't be able to produce some when you are. That's why Yiyi's sperm is still usable in the present time.
When Fenfeng said he deposited an embryo for Yiyi, he means he requested the lab to process Yiyi's sperm with an egg, to form an embryo to freeze and store, until they are both are ready to give Rourou a sibling. Yey!
But but but. Fengfeng's psycho aunt stole the said embryo and pushed the process until it became BigHead here.
OH NO BABY ITS NOT RUDE, GO ON. GO ON A DATE.