The already-unusual legal battle over Modern Family actress Sofía Vergara’s frozen embryos reached a surprising new chapter on Tuesday — when the embryos sued Vergara. Yes: Two unborn, un-gestated frozen pre-embryos became the plaintiffs in a right-to-live lawsuit. How is this possible? How common is it? And what does it all mean legally? Here’s what to know.Like many couples engaging in assisted reproduction, Vergara and then-fiancé Nick Loeb used in vitro fertilization (IVF) to create pre-embryos. (Jargon note: Some, especially on the right-to-life side, prefer the term “early embryo” because they think the term “pre-embryo” devalues the entities. I use the term that is most common in the law without intending to take sides on who has the better terminology or attaching much weight to it.) More specifically, Vergara’s eggs were harvested and combined outside the body with Loeb’s sperm to produce embryos that could then be implanted into a uterus to hopefully produce a successful pregnancy.In most IVF clinics in America, before IVF or freezing is performed, the couple is asked to specify in writing their “dispositional preference” for the pre-embryos — that is, what should be done with them in the event the couple splits up, or one or both parties die. Among the common options are donating the pre-embryo to research, destroying the pre-embryo, making the pre-embryo available to the male partner to use for reproduction with another woman, making the pre-embryo available to the female partner for reproduction, or indefinite freezing.According to Page Six, a First Amended Complaint filed originally in California court pertaining to this case (Refinery29 was unable to obtain court filings by press time, so I have tried to explain the situation more generally and refrain from commenting directly on the merits of this case) suggests that Vergara and Loeb initially did a first round of IVF, successfully fertilized some eggs to create pre-embryos, and attempted to implant them in a surrogate mother. While many women undergo IVF intending to carry the baby to term themselves, others use a surrogate. In this instance we would call the woman a “gestational” surrogate to denote that the surrogate is carrying the child but is not its genetic mother — that would be Vergara. The initial attempts at surrogacy were unsuccessful. The couple allegedly conducted another round of IVF, froze the resulting pre-embryos for later use in a surrogate, but their relationship ended before they could find a new surrogate to work with.That breakdown has resulted in this legal case, with the media reporting that Loeb is suing for the right to have two of the frozen embryos (which he apparently has named Isabella and Emma, according to Page Six) implanted in a surrogate. He has framed his claims in the language of the right-to-life movement, claiming that these are his “children” and they have a right to live.Vergara, for her part, according to press reports , has claimed that “the genetic material was created pursuant to a written agreement that required both parties’ written consent to attempt to create a pregnancy,” and that since she refuses that consent now, Loeb should not be allowed to use the pre-embryos for reproduction.