Over decades diazoalkenes (R2C=C=N2) were postulated as reactive intermediates in organic chemistry even though their direct spectroscopic detection proved very challenging. In the 1970/80ies several groups probed their existence mainly indirectly by trapping experiments or directly by matrix‐isolation studies. In 2021, our group and the Severin group reported independently the synthesis and characterization of the first room‐temperature stable diazoalkenes, which initiated a rapidly expanding research field. Up to now four different classes of N‐heterocyclic substituted room‐temperature stable diazoalkenes have been reported. Their properties and unique reactivity, such as N2/CO exchange or utilization as vinylidene precursors in organic and transition metal chemistry are presented. This review summarizes the early discoveries of diazoalkenes from their initial postulation as transient, elusive species up to the recent findings of the room‐temperature stable derivatives. Early discoveries of diazoalkenes (R2C=C=N2) in organic synthesis and the identification of room‐temperature‐stable diazoalkenes since 2021 are summarized in this Minireview. The synthesis, properties, and reactivity of this novel molecule class are presented, and its use in organic synthesis, main‐group, and transition‐metal chemistry highlighted.