The drug central to Breaking Bad is methamphetamine—commonly called meth or crystal meth—portrayed in the series as a distinctive blue crystalline product nicknamed "Blue Sky." Chemically, it’s methamphetamine hydrochloride, a powerful, highly addictive stimulant. Illegal manufacture, distribution, and use of meth carry severe health risks, high addiction potential, and serious legal consequences.

Methamphetamine’s IUPAC (full) chemical name is N‑methyl‑1‑phenylpropan‑2‑amine (often written as (RS)-N‑methyl‑1‑phenylpropan‑2‑amine). Its molecular formula is C10H15N. It is also called methylamphetamine or desoxyephedrine and exists as enantiomers; the S-(+)-enantiomer (dextromethamphetamine) is the more pharmacologically active central nervous system stimulant, with high abuse potential and limited medical uses.

True methamphetamine use causes positives, but other causes include prescription stimulants (amphetamine salts, methylphenidate, prescribed methamphetamine), illicit drugs like MDMA, OTC decongestants (pseudoephedrine, ephedrine), certain antidepressants (bupropion, trazodone) and Parkinson’s drug selegiline. Immunoassay cross‑reactivity, laboratory error, contamination or passive exposure can give false positives; confirmatory GC‑MS/LC‑MS testing is recommended.

Few prescription drugs are metabolized to methamphetamine. Selegiline (an MAO‑B inhibitor) is converted in the body to L‑methamphetamine and L‑amphetamine. Benzphetamine (an anorectic) can yield methamphetamine/amphetamine metabolites. Ephedrine and pseudoephedrine are precursors that may cause false‑positive methamphetamine screens and can be chemically converted illicitly, but aren’t direct therapeutic sources of methamphetamine.

I don’t have enough context to know which "Jesse" you mean. Several fictional and real people named Jesse have injected different drugs (for example, Jesse Pinkman injected heroin in Breaking Bad). Which Jesse are you referring to—specify the show, episode, article, or news story—and I’ll give a concise, sourced answer.

Methylamine is an industrial chemical and basic building block used as an intermediate in organic synthesis. It’s used to make pharmaceuticals, agrochemicals, dyes, rubber chemicals, solvents and certain surfactants, and in laboratory reagent applications. It also appears as a reported precursor in illicit drug manufacture, so its handling and sale are regulated and controlled in many jurisdictions.