Basidiocarps usually collybioid or mycenoid, more rarely tricholomatoid or omphalinoid.
Section Cyanula often with steel grey to blue to midnight blue or blue-black pigments.
Section Leptonia often with browner or yellow-brown coloration, but also with bluish pigments in some members.
Other taxa have rosy, pink, or pale coloration.
Pileus dry, densely tomentulose at the disc and outwards squamulose to appressed squamulose or apressed-scaly with a glabrous at the margin in Section Cyanula.
Smooth or most often radially fibrillose to scaly to apressed squamulose in Section Leptonia. Margin sometimes striate (taxonomically important) or translucent striate. Pigmentation may change dramatically from youth to maturity.
Lamellae thin, close to more well spaced, sometimes venose, usually adnate, sometimes adnexed or seceding, rarely decurrent. Pale, sometimes with a bluish cast, sometimes aging yellowish (taxonomically important), sometimes with an uneven margin, sometimes with a darkened margin (very taxonomically significant).
Stipe grey, bluish, tan to yellow-brown to pallid (taxonomically important). Smooth to scaly or densley fibrillose (taxonomically important), hollow, sometimes with a prominent boot of mycelial tomentum, staining reactions of this mycelium may be taxonomically important.
Macrochemical reactions obscure and rarely taxonomically important.
Pileipellis often a trichodermium at the disc and a cutis with transitions to a trichoderm outwards, also often a palisade-trichoderm (hymeniderm). In Section Leptonia either with clamps or with elements (sometimes rounded) in distinct chains (ie. submoniliform or a calliderm). Usually discoloring to wine brown or red-brown in KOH, diagnostically remaining blue in Leptonia carnea. Usually with intracellular pigmentation, sometimes encrusted (should be viewed in a saturated sugar or salt solution).
Lamellar trama subparallel, with reflective granules.
Basidia typically clavate and 4-spored, sometimes 2-spored (important), not often of great taxonomic importance.
Spores distinctly 5-7 angular with prominent hilar appendage, usually heterodiametric (high Q value). Length taxonomically important (> or < 10 microns).
Pleurocystidia usually absent.
Cheilocystidia sometimes present, sometimes pigmented, of taxonomic importance, tibiiform to capitate in Section Rhamphocystotae.
Caulocystidia often present as clavate to irregularly cylindrical or flexuous hyphae.
Presence/absence of clamps of taxonomic importance.