Solanaceae (the nightshade or potato family) is one of the most economically important plant families, containing approximately 2,700 species in about 98 genera, distributed worldwide but particularly diverse in South America. The family is renowned for producing important food crops (potato, tomato, chilli, brinjal), medicinal plants (Atropa, Datura, Withania), and ornamental plants (Petunia, Salpiglossis). Many Solanaceae produce alkaloids — including solanine (in green/sprouting potatoes), nicotine (tobacco), atropine and scopolamine (Atropa, Datura), and capsaicin (chilli) — which have both toxic and medicinal properties. The family belongs to the order Solanales.

The floral formula of Solanaceae is: ⊕ ♀ K(5) C(5) A5 G(2̄). ⊕ = actinomorphic (radially symmetrical, though some genera like Solanum can be slightly irregular). ♀ = bisexual. K(5) = 5 sepals, gamosepalous (fused), persistent (remain on fruit). C(5) = 5 petals, gamopetalous (fused into a tube or rotate/wheel-shaped corolla), variously shaped: tubular (Nicotiana), rotate/wheel-shaped (Solanum tomato, potato), bell-shaped (Atropa), trumpet-shaped (Datura). A5 = 5 stamens, epipetalous (attached to corolla tube), usually with large anthers that often form a cone around the style (as in tomato — the stamens form a yellow anther cone). G(2̄) = 2 carpels, syncarpous (fused), superior ovary (hypogynous), bilocular, axile placentation, usually with many ovules.

Solanaceae produces two main fruit types: Berry: the most common type — a fleshy fruit with a thin outer skin (epicarp), fleshy mesocarp, and seeds embedded in a pulpy endocarp. Examples: tomato (red berry), brinjal (purple berry), Solanum nigrum (black berry), Withania (orange-red berry enclosed in persistent inflated calyx). Capsule: a dry, dehiscent fruit that splits open at maturity to release seeds. Examples: Datura (spiny capsule — called a thorn apple), Nicotiana (capsule), Petunia (capsule). In some Solanaceae, the persistent calyx enlarges and forms a papery bladder (physalis) enclosing the fruit, as in Cape gooseberry (Physalis peruviana). The persistent calyx (which remains on the fruit) is a diagnostic feature of the family.

Solanaceae is one of the richest plant families in terms of medicinally and toxicologically important alkaloids, which are nitrogen-containing secondary metabolites. Tropane alkaloids: Atropine and hyoscyamine (from Atropa belladonna — deadly nightshade): anticholinergic drugs used to dilate pupils (ophthalmic use), treat bradycardia, organophosphate poisoning antidote, and reduce secretions before surgery. Scopolamine (from Datura, Hyoscyamus): used for motion sickness prevention (transdermal patch), pre-anaesthetic medication. Pyridine alkaloids: Nicotine (from Nicotiana tabacum — tobacco): binds nicotinic acetylcholine receptors; used as insecticide (neonicotinoids derived from it); highly addictive. Steroidal alkaloids: Solanine and chaconine (from sprouting/green potatoes): toxic glycoalkaloids; responsible for green potato toxicity. Capsaicin (from Capsicum): technically not an alkaloid but a vanilloid; responsible for chilli's pungency; used in pain management creams (desensitises TRPV1 receptors).