Nested Blue is a Basic Blooncard in Bloons Card Storm. It spawns a Red Bloon if it is destroyed, which does not inherit any modified properties of its parent (e.g. its Delay or being On Fire). It can be summoned by the Nested Green, which itself can be summoned by a Nested Yellow.
Nested Blues have the same cost and HP as normal Blue Bloons except have only 1 charge, 1 delay, but can spawn extra bloons. However, the total HP from a Nested Blue card is less than a normal Blue Bloon (90 HP instead of 100 HP), and possesses the most bloons per Gold (excluding 0 Gold Bloons).
The extra Red Bloon inside forces the opponent to carefully pop the Nested Blue, rather than rely on high single-target damage.
Compared to the other Nested Bloons, playing a Nested Blue is easier early on due to cost, but is a poor choice to begin if the opponent has Dart Monkey Twins. Additionally, its HP is unable to survive two Spike Storm! outside of Dark Castle (poor candidate for Bloon Embiggen strategies), and its Rare rarity may block Rare Power draws of better cards. Instead, for combos, it stands out as a cost-effective feed for Bolstered Bloon.
Most of the Nested Blue's strengths derive from its powerful parents, the Nested Green and Nested Yellow.