Greetings, In Unity 5.4, we have finally begun the process of removing the Legacy Particle System from Unity. The Legacy Particle System classes (ParticleEmitter, ParticleAnimator, ParticleRenderer, etc) have been marked as [Obsolete] in the API, and using them in the Inspector will now display a warning message. We have also begun work on reducing the number of packages in the Asset Store which are using the Legacy Particle System. If your project is still using the Legacy Particle System, you should upgrade your effects to use the newer ParticleSystem component soon. (We're exploring whether we can create some kind of automatic upgrader tool, but we cannot promise anything). If you're using the Legacy Particle System via packages that you obtained from the Asset Store, we recommend monitoring the store for new versions of your packages. We will be encouraging Asset Store authors who have Legacy particle effect packages to update their effects as soon as they can. We don't have a fixed date for when the Legacy Particle System will be removed; instead we're going to monitor how widely it is still being used, and try to wait until that's dropped to a sufficiently low level. (But we're not going to wait forever). A lot of effort has gone into improving the new ParticleSystem over recent Unity 5 releases - through removing limitations such as the lack of API for system properties, through new features such as the Trigger module in 5.4, and through general performance optimizations such as multithreading support. At this point we believe there is nothing you can do with the Legacy Particle System that you cannot also do with the new ParticleSystem. But, we never know about all the use cases out there. If you're currently using the Legacy Particle System and cannot upgrade to the new ParticleSystem component because of technical limitations, please reply to this thread and explain what's blocking you.