Being coached by a treasure like former Kirov prima Irina Kolpakova is an experience most dancers only dream of. But company members at American Ballet Theatre have been the lucky beneficiaries of her wisdom since 1990. Thanks to Instagram, where pros like Gillian Murphy and James Whiteside share snippets of their sessions with Kolpakova, any ballet lover can be a fly on the wall during rehearsals with the famed ballet mistress.