diff --git a/playground/element/index.html b/playground/element/index.html
index bb77d2110..681591601 100644
--- a/playground/element/index.html
+++ b/playground/element/index.html
@@ -8,17 +8,17 @@
 </head>
 
 <body>
-  <swiper-container>
-    <swiper-slide>Slide 1</swiper-slide>
-    <swiper-slide>Slide 2</swiper-slide>
-    <swiper-slide>Slide 3</swiper-slide>
-    <swiper-slide>Slide 4</swiper-slide>
-    <swiper-slide>Slide 5</swiper-slide>
-    <swiper-slide>Slide 6</swiper-slide>
-    <swiper-slide>Slide 7</swiper-slide>
-    <swiper-slide>Slide 8</swiper-slide>
-    <swiper-slide>Slide 9</swiper-slide>
-    <swiper-slide>Slide 10</swiper-slide>
+  <swiper-container effect="cube">
+    <div slot="slide-0">Slide 1</div>
+    <div slot="slide-1">Slide 2</div>
+    <div slot="slide-2">Slide 3</div>
+    <div slot="slide-3">Slide 4</div>
+    <div slot="slide-4">Slide 5</div>
+    <div slot="slide-5">Slide 6</div>
+    <div slot="slide-6">Slide 7</div>
+    <div slot="slide-7">Slide 8</div>
+    <div slot="slide-8">Slide 9</div>
+    <div slot="slide-9">Slide 10</div>
   </swiper-container>
   <style>
     body,
@@ -35,7 +35,7 @@
       margin: 50px auto;
     }
 
-    swiper-slide {
+    swiper-container::part(slide) {
       background: #f1f1f1;
       color: #000;
       text-align: center;
diff --git a/src/components-shared/get-params.mjs b/src/components-shared/get-params.mjs
index c0b4d820d..436c59abb 100644
--- a/src/components-shared/get-params.mjs
+++ b/src/components-shared/get-params.mjs
@@ -1,6 +1,6 @@
-import { Swiper } from '../swiper.mjs';
 import { isObject, extend } from './utils.mjs';
 import { paramsList } from './params-list.mjs';
+import defaults from '../core/defaults.mjs';
 
 function getParams(obj = {}, splitEvents = true) {
   const params = {
@@ -8,8 +8,7 @@ function getParams(obj = {}, splitEvents = true) {
   };
   const events = {};
   const passedParams = {};
-  extend(params, Swiper.defaults);
-  extend(params, Swiper.extendedDefaults);
+  extend(params, defaults);
   params._emitClasses = true;
   params.init = false;
 
diff --git a/src/core/core.mjs b/src/core/core.mjs
index f95647227..d21749a8e 100644
--- a/src/core/core.mjs
+++ b/src/core/core.mjs
@@ -514,7 +514,7 @@ class Swiper {
     Object.assign(swiper, {
       el,
       wrapperEl,
-      slidesEl: swiper.isElement ? el.parentNode.host : wrapperEl,
+      slidesEl: swiper.isElement && !el.parentNode.host.slideSlots ? el.parentNode.host : wrapperEl,
       hostEl: swiper.isElement ? el.parentNode.host : el,
       mounted: true,
 
diff --git a/src/core/modules/observer/observer.mjs b/src/core/modules/observer/observer.mjs
index a74d025cf..c8acf3271 100644
--- a/src/core/modules/observer/observer.mjs
+++ b/src/core/modules/observer/observer.mjs
@@ -38,13 +38,13 @@ export default function Observer({ swiper, extendParams, on, emit }) {
   const init = () => {
     if (!swiper.params.observer) return;
     if (swiper.params.observeParents) {
-      const containerParents = elementParents(swiper.el);
+      const containerParents = elementParents(swiper.hostEl);
       for (let i = 0; i < containerParents.length; i += 1) {
         attach(containerParents[i]);
       }
     }
     // Observe container
-    attach(swiper.el, {
+    attach(swiper.hostEl, {
       childList: swiper.params.observeSlideChildren,
     });
 
diff --git a/src/swiper-element.mjs b/src/swiper-element.mjs
index 5d6dc3c35..98c0991b0 100644
--- a/src/swiper-element.mjs
+++ b/src/swiper-element.mjs
@@ -65,11 +65,43 @@ class SwiperContainer extends ClassToExtend {
     return this.injectStylesUrls || [];
   }
 
+  calcSlideSlots() {
+    const currentSideSlots = this.slideSlots || 0;
+    // slide slots
+    const slideSlotChildren = [...this.querySelectorAll(`[slot^=slide-]`)].map((child) => {
+      return parseInt(child.getAttribute('slot').split('slide-')[1], 10);
+    });
+    this.slideSlots = slideSlotChildren.length ? Math.max(...slideSlotChildren) + 1 : 0;
+    if (!this.rendered) return;
+    if (this.slideSlots > currentSideSlots) {
+      for (let i = currentSideSlots; i < this.slideSlots; i += 1) {
+        const slideEl = document.createElement('swiper-slide');
+        slideEl.setAttribute('part', `slide slide-${i + 1}`);
+        const slotEl = document.createElement('slot');
+        slotEl.setAttribute('name', `slide-${i + 1}`);
+        slideEl.appendChild(slotEl);
+        this.shadowRoot.querySelector('.swiper-wrapper').appendChild(slideEl);
+      }
+    } else if (this.slideSlots < currentSideSlots) {
+      const slides = this.swiper.slides;
+      for (let i = slides.length - 1; i >= 0; i -= 1) {
+        if (i > this.slideSlots) {
+          slides[i].remove();
+        }
+      }
+    }
+  }
+
   render() {
     if (this.rendered) return;
 
+    this.calcSlideSlots();
+
     // local styles
-    const localStyles = this.cssStyles();
+    let localStyles = this.cssStyles();
+    if (this.slideSlots > 0) {
+      localStyles = localStyles.replace(/::slotted\(([a-z-0-9.]*)\)/g, '$1');
+    }
     if (localStyles.length) {
       addStyle(this.shadowRoot, localStyles);
     }
@@ -86,11 +118,17 @@ class SwiperContainer extends ClassToExtend {
     const el = document.createElement('div');
     el.classList.add('swiper');
     el.part = 'container';
+
     // prettier-ignore
     el.innerHTML = `
       <slot name="container-start"></slot>
       <div class="swiper-wrapper" part="wrapper">
         <slot></slot>
+        ${Array.from({length: this.slideSlots}).map((_, index) => `
+        <swiper-slide part="slide slide-${index}">
+          <slot name="slide-${index}"></slot>
+        </swiper-slide>
+        `).join('')}
       </div>
       <slot name="container-end"></slot>
       ${needsNavigation(this.passedParams) ? `
@@ -117,12 +155,18 @@ class SwiperContainer extends ClassToExtend {
     delete this.swiperParams.init;
 
     this.render();
+
     // eslint-disable-next-line
     this.swiper = new Swiper(this.shadowRoot.querySelector('.swiper'), {
+      ...(swiperParams.virtual
+        ? {}
+        : { observer: true, observeSlideChildren: this.slideSlots > 0 }),
       ...swiperParams,
       touchEventsTarget: 'container',
-      ...(swiperParams.virtual ? {} : { observer: true }),
       onAny: (name, ...args) => {
+        if (name === 'observerUpdate') {
+          this.calcSlideSlots();
+        }
         const eventName = swiperParams.eventsPrefix
           ? `${swiperParams.eventsPrefix}${name.toLowerCase()}`
           : name.toLowerCase();
